Almost nobody goes to Thailand and stays in one place. The standard trip is Bangkok for a few days, an island or the north for a week or two, and very often a hop over a border and back. Each of those three asks something different of a phone: dense city navigation, patchy coverage on water, and a fresh piece of immigration paperwork at the frontier. That is the useful way to choose a plan, and it is not how the plan grid is laid out. Thailand is sold in thirteen different combinations of data and days, and the grid sorts them by price rather than by the trip they suit. Inside it, the same fifty gigabytes appears three times at three wildly different prices, a week of unlimited costs more than a whole twenty-gigabyte month, and one plan runs for ten days and cannot be topped up at all. Price, unusually, is not the variable. At the sizes most travellers buy, Thailand sits on the lowest step we sell, tied with more than fifty other destinations, so the difference between a cheap seller and an expensive one is pennies. The difference between the right row and the wrong one is several times that. This guide walks the range in the order the trip happens: the arrival card first, then the plan, then the border.
The paperwork that comes before the plan
Thailand retired its paper arrival slip in May 2025 and replaced it with a digital arrival card. Every foreign passport holder entering by air, land or sea is now expected to file one. The exceptions are narrow: passengers transiting without clearing immigration, and people entering on a border pass. It is not a visa, it costs nothing, and it takes a few minutes — but arriving without it is a queue you did not have to stand in, at the end of a long flight.
Three details are worth knowing before you start. The submission window opens seventy-two hours before you arrive, so it cannot be filed weeks ahead with the rest of your travel admin. It asks for your passport details, your flight and the address of your first night, so you want your booking open in front of you. And it is filed per entry, which matters more than it sounds: a few days in Laos or Cambodia in the middle of your trip means filing a second one for the way back in.
The form is free on the Thai Immigration Bureau's own website. Look-alike sites charge a fee to complete a free government form and they advertise hard against the obvious searches, so check where you have landed before typing a passport number into anything.
The reason this comes first in a guide about data is that it sets the order of everything else. A surprising amount of arrival admin cannot be done offline or on a foreign line. Anything that verifies you by text message wants your usual number in normal service, so ride-hailing accounts, messaging apps and banking apps should be set up at home, days before you fly, rather than in an arrivals hall. Save your accommodation address and your arrival card confirmation somewhere you can reach without a connection.
Then install the eSIM at home over wifi and leave the line switched off. It does not start counting anything until it first connects to a Thai network, so there is no cost to installing early and no reason to wait. Landing at Suvarnabhumi or Don Mueang you want to be walking towards immigration with the confirmation already on your screen.
- The digital arrival card is required of foreign passport holders arriving by air, land or sea.
- The window opens seventy-two hours before arrival, and it needs your flight and your first night's address.
- It is per entry — a side trip to a neighbour means filing again on the way back.
- It is free on the official immigration site; paid look-alikes exist.
- Install the eSIM at home and leave it off. Nothing starts until it first connects in Thailand.
Where the data actually goes: maps, piers and the evening upload
Thailand has a distinctive data pattern, and it is not the one people budget for. Very little of it is streaming, because you are outdoors. Almost all of it is short, constant bursts of maps, messaging and ride-hailing. You will open maps to find a soi you cannot see from the main road, again to find which of several piers your boat leaves from, and again to work out which exit at a Bangkok interchange station puts you on the right side of eight lanes of traffic. You will message a guesthouse to say your flight moved. You will point a translation app at a menu.
High frequency, low volume. That is why so many people come home from a fortnight in Thailand having used far less than they feared. The exception is video, and it is a big one: a couple of evenings of catch-up television in a hotel room, or letting a phone back up a day of footage to the cloud over mobile data instead of hotel wifi, can outweigh everything else on the trip put together.
Two people travelling together changes the maths in a way worth planning for. One plan shared over a hotspot is usually cheaper than two, because the next size up costs less than a second plan of the size below. The trade is that one phone carries the whole allowance and the whole battery drain, and the connection walks away when that person goes to get a coffee. Couples who stay together: one plan and a hotspot. Friends who split up during the day: two plans.
There is one thing not worth budgeting for at all, and that is overage. A fixed plan does not bill you when it runs out. It stops. The cost of guessing low is an interruption and a top-up, never a surprise on a statement, and since a top-up adds days as well as data, guessing low is the cheap mistake. Guessing high is the expensive one.
- Maps, messaging and ride-hailing all day: frequent, but small.
- One evening of streaming, or one cloud backup of a day's video, can outweigh the whole rest of the trip.
- A fortnight of ordinary use lands most travellers under five gigabytes.
- Two people on one hotspot is usually cheaper than two plans — until they split up during the day.
- Running out costs an interruption, never an overage charge. Guessing low is the cheap mistake.
The same fifty gigabytes, sold three different ways
This is the most useful thing to know about the Thailand range, and it is invisible until you line the plans up side by side. Fifty gigabytes is sold here with three different windows — ten days, thirty days, and one hundred and eighty days — and the three are not priced anywhere near each other.
The ten-day version is the best value large plan in Thailand and nothing else is close. Per gigabyte it costs a bit over a quarter of what the other two cost, and in cash terms it is only a few per cent more than the twenty-gigabyte month, for two and a half times the data. There are two catches and both are real. Ten days is short for the classic Thailand trip. And this is one of a tiny handful of multi-day plans in our entire catalogue that cannot be topped up, which the plan card flags with a No top-ups badge. Burn through it on day six and you buy a second eSIM rather than adding to this one.
The thirty-day version is the poorest value row in the Thailand range, and there is a quick way to see it. Divide its price by fifty gigabytes and you get the same cost per gigabyte as the five-gigabyte month. Ten times the data for ten times the money, with no volume discount whatsoever — which is not how any other size in the Thailand range is priced. It also costs considerably more than the identical fifty-gigabyte month costs for Malaysia, Singapore or Indonesia, which is a genuine oddity in a country that is otherwise on the cheapest step.
The six-month version costs only a few per cent more than the thirty-day one for six times the window, so if those two are your shortlist the answer is not the shorter one. Its real audience is different, though. It is the plan for someone who comes to Thailand more than once a year, because the six-month clock starts at first connection rather than at purchase, and one eSIM can carry two or three trips inside it.
So: if your trip fits inside ten days and you use a lot of data, take the ten-day fifty and enjoy it. If it does not fit, skip both larger fifties entirely and buy the twenty-gigabyte month, which costs less than the ten-day plan and runs three times as long.
- Ten-day fifty: a bit over a quarter of the others' cost per gigabyte, but a short window and no top-ups.
- Thirty-day fifty: priced per gigabyte exactly like the five-gigabyte month, so there is no volume discount at all.
- Six-month fifty: a few per cent more than the thirty-day, six times the window, and the right buy for a repeat visitor.
- If ten days is too short, the twenty-gigabyte month costs less again and lasts thirty.
The week-long plan that costs more than a month
The small end of the Thailand range holds a trap that catches people who are being careful with money. The one-gigabyte week costs about a fifth less than the three-gigabyte month. For that fifth you hand back two thirds of the data and more than three quarters of the window. It is the most common wrong buy we see anywhere, and it happens because a smaller number reads as the safer choice when you have no idea yet how much you will need.
The single-day plan below it works differently and deserves a fairer hearing. It carries two gigabytes for one calendar day, it cannot be topped up, and two of them cost about the same as the entire five-gigabyte month. Bought for a holiday it is dreadful value. Bought for what it is actually for, it is exactly right: Bangkok is one of Asia's great connecting airports, and a single overnight between long-haul flights needs a ride to a hotel, a message to say you landed and nothing else whatsoever.
Between those two extremes there is a step worth knowing about. Going from the five-gigabyte month to the ten costs about half as much again and doubles the data, which is the most generous upgrade in the whole Thailand ladder. If you are hesitating between those two sizes, the larger one is cheap enough that hesitating is not worth your time.
For anything longer than a weekend, the three-gigabyte month is the floor. It costs barely more than the one-gigabyte week and leaves you room to be wrong about your own usage, which on a first trip to Thailand you almost certainly will be.
- The one-gigabyte week costs about a fifth less than the three-gigabyte month, for a third of the data and under a quarter of the window.
- The single-day plan cannot be topped up, and two days of it cost about a whole five-gigabyte month.
- It is the right buy for one thing only: a single overnight in transit through Bangkok.
- Five gigabytes to ten costs about half as much again and doubles the data — the best step in the range.
Unlimited is beaten here by the plans it usually beats
Unlimited plans in Thailand behave the way ours behave everywhere: a generous full-speed allowance each day, then reduced speed until the day resets. The reset runs twenty-four hours from your first connection rather than from local midnight, which is worth remembering if you switch the line on at two in the morning at the airport. In a country where fixed data is expensive, that product is excellent value. Thailand is not that country.
A week of unlimited costs about three fifths more than a whole twenty-gigabyte month, and the month runs four times as long. It also costs about half as much again as the ten-day fifty, which carries more data than most people could get through in a week if they tried. A month of unlimited costs about three fifths more than the fifty-gigabyte month.
Even the three-day unlimited, which looks cheap sitting next to the twenty-gigabyte month, does not survive inspection. Its ceiling across three days is less data than the ten-gigabyte month carries, and the ten-gigabyte month costs less than it does and lasts ten times longer.
There is one traveller for whom unlimited is right, and it is a real case rather than a courtesy. If you are working from Thailand — tethering a laptop through the day, on video calls, pushing footage up every evening — you will pass the point where a fixed plan can even reach, because the largest fixed month tops out at fifty gigabytes. That crossover sits somewhere above a gigabyte and a half a day, sustained, every day. Below it, unlimited in Thailand is the most expensive way to buy less data than you expected.
Either way, hotspot use draws from the same allowance rather than a separate one, on both kinds of plan. Nothing is held back for tethering and nothing extra is charged for it.
- A week of unlimited costs about three fifths more than a twenty-gigabyte month that lasts four times longer.
- The three-day unlimited has a lower ceiling than the ten-gigabyte month, which costs less again.
- The crossover is around a gigabyte and a half a day, sustained — remote workers, not holidaymakers.
- Hotspot data comes out of the same allowance on fixed and unlimited alike.
The border hop, and what it does to your plan
Thailand is the hub of a region people cross constantly, and this is where a country plan stops being the obvious answer. A Thailand plan covers Thailand. Cross into Cambodia and it has nothing to connect to, at exactly the moment you are trying to read a border form and find onward transport. There are two sensible regional answers, and the choice between them is settled almost entirely by whether Vietnam is on your route.
The three-country list covering Singapore, Malaysia and Thailand is the best-value multi-country plan we sell anywhere in Asia. At the same size it costs about half as much again as a Thailand plan alone, which means it beats buying any two of those three separately, at every size we offer. Singapore for a few days then Bangkok, or Bangkok down the peninsula to Kuala Lumpur, and there is nothing to think about.
The seven-country Southeast Asia list covers Cambodia, Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam. It costs about two and a half times a Thailand plan, so as a rule it earns its keep from three countries onward. Vietnam is the exception that moves the line: it costs roughly double what Thailand costs on its own, so once Vietnam is on the route the seven-country list wins from just two countries, at every size.
Laos is on neither list. For the classic overland loop through Thailand, Cambodia and Laos, the practical buy is the seven-country list plus a small Laos plan for the days you are actually there. The much wider Asia lists cost around four and a half times a Thailand plan and only earn that if Japan, South Korea, China, Hong Kong or India is on the itinerary. A global list costs several times a Thailand plan and is almost never the right answer for a trip that stays in Southeast Asia.
Whatever you buy, remember what the first section said: you file a fresh arrival card every time you re-enter Thailand, and border days are precisely the days you least want to be offline. Make sure whatever you are carrying covers the day you come back in, not only the days you are on a beach.
- Singapore, Malaysia and Thailand: the three-country list beats any two of them bought separately, at every size.
- Add Cambodia, Indonesia, the Philippines or Vietnam and look at the seven-country Southeast Asia list.
- It wins from three countries — or from two if Vietnam is one, because Vietnam alone costs about double Thailand.
- Laos is on neither list. Pair the seven-country list with a small Laos plan.
- Every re-entry into Thailand means a new arrival card, so keep data live on border days.
Islands, ferries and the north: where Thailand goes quiet
Two networks matter in Thailand. AIS and True between them carry almost the whole market, both run 5G across Bangkok, the main tourist islands and the large northern cities, and a travel eSIM connects to them the way any visiting phone does. True absorbed dtac in 2023, so if you open your phone's network list and find a dtac entry sitting beside a True one, that is the same company. The state-owned operator NT is a distant third and largely runs on the other two networks.
That matters for one narrow purpose. If your data has gone sluggish in a particular spot, opening the network list and picking a different operator by hand sometimes helps, because you are choosing between networks that all already reach you rather than conjuring coverage where there is none. In Bangkok or Phuket you will usually have that choice. On a mountain road towards Pai you often will not, and no amount of switching invents a signal.
Which brings us to the honest part, because it is the question this section really exists to answer. No plan tier and no seller changes coverage. Where Thailand thins out it thins out for everybody: open water between islands, long-tail boats, the interior of national parks, the hill roads in the north. Close to shore you will generally be fine. Halfway across on a ferry, assume not.
The fix is not a bigger plan. It is downloading offline maps for the islands and the mountains before you leave a city with good coverage, and screenshotting boat times and pier names rather than trusting that you can reload them standing on a jetty. This is the one piece of Thailand advice that has not changed in fifteen years and is not going to.
- AIS and True carry almost the whole Thai market, both with 5G where visitors go.
- dtac is part of True now, so seeing both names in the network list is normal.
- Manual network selection only helps where more than one network already reaches you.
- Open water, long-tail boats, national parks and northern hill roads go quiet for everyone.
- Offline maps and screenshotted ferry times solve more of that than any plan size.
No counter, no passport photograph, no local number
Buying a Thai SIM card is not like buying one at home. Thai regulation requires every SIM to be registered against identification — for a visitor, that means handing your passport across a counter to be photographed and uploaded against the number you are about to use. The identity checks around that process have been getting stricter rather than looser, with operators moving towards biometric verification at the point of sale.
A travel eSIM does not go through any of it. It connects as a visiting line rather than a Thai subscription, so there is no counter, no photocopy, no form and no queue at an arrivals-hall kiosk while your driver waits. For a short trip that is most of the argument, and it is a bigger deal in Thailand than in most places precisely because the registration step there is not a formality.
The trade-off is exactly what you would expect, and we would rather say it than let you find out. You do not get a Thai number. Anything that insists on one — a Thai bank app, a service that will only send a code to a number starting with the Thai country code — will not work through the eSIM. What you keep instead is your own number, still live on your home SIM beside the eSIM, still receiving the codes your bank and your usual apps send you. For most travellers that is the trade they actually want, but it is a trade.
There is a second limit worth naming. Most Thailand rows run for thirty days. If you are staying two or three months, a travel eSIM stops being the sensible answer somewhere in the middle of that, and a local prepaid package becomes cheaper. The six-month fifty-gigabyte plan is built for a series of short visits, not for one long stay. We would rather point at where the product runs out than sell you the wrong shape twice.
- Thai SIM cards must be registered against photographed identification, and those checks are tightening.
- A travel eSIM skips the counter entirely, because it is not a Thai subscription.
- The cost of that is no Thai number, so nothing that demands one will work.
- Your own number stays live on your home SIM for verification codes.
- Most rows run thirty days; a stay of several months is a local-plan problem, not an eSIM one.
If you only read one section: pick your trip
Everything above, compressed into the trips people actually book. Each assumes one phone, maps and messaging through the day and no habitual streaming. If you stream in the evenings, move up one tier from whatever is listed.
One last thing, and it is the part people skip. In the week before you fly, buy and install the eSIM and leave the line switched off, set up any app that verifies you by text message while your usual number is still in normal service at home, download offline maps for anywhere beyond the cities, and file the arrival card once you are inside the seventy-two-hour window. Then when the wheels touch down, switch the line on, turn data roaming on for it, and you are connected before the immigration hall.
- One overnight in transit through Bangkok: the single-day plan, and nothing more.
- Long weekend in Bangkok: the three-gigabyte month.
- The classic ten days, Bangkok plus an island: the five-gigabyte month.
- Ten days as a heavy user, uploading video daily: the ten-day fifty, if you can live inside its window and its lack of top-ups.
- Two to three weeks island-hopping or heading north: the ten-gigabyte month.
- A month in one place, or a couple sharing one hotspot: the twenty-gigabyte month.
- Working remotely from Thailand for a month: unlimited, or the twenty-gigabyte month topped up as you go.
- Coming back two or three times this year: the fifty-gigabyte plan with the six-month window.
- Thailand plus Singapore or Malaysia: the three-country list.
- Thailand plus Vietnam, or three countries in Southeast Asia: the seven-country list.
- Thailand, Cambodia and Laos overland: the seven-country list plus a small Laos plan.
Frequently asked questions
How much data do I need for two weeks in Thailand?
Five gigabytes covers a fortnight comfortably for most travellers. Thai trips are heavy on maps, messaging and ride-hailing and light on streaming, because the days are spent outside. Move up to ten gigabytes if you tether a laptop in the evenings, back photos and video up over mobile data rather than hotel wifi, or watch anything regularly. Guessing low is the cheap mistake: nothing is billed when a plan runs out, and a top-up adds days as well as data.
What is the cheapest eSIM for Thailand?
At the sizes most people buy, Thailand sits on the lowest price step we sell, shared with more than fifty other destinations, so any honest seller's Thailand plan is within pennies of another's at the same size. The cheapest row on the page is the single-day plan, but it only makes sense for one overnight. For a real trip the cheapest sensible start is the three-gigabyte month, which costs barely more than the one-gigabyte week and lasts four times as long.
Do I need to fill in the Thailand Digital Arrival Card before I fly?
Yes, if you hold a foreign passport and are entering by air, land or sea. It replaced the paper arrival slip in May 2025. The submission window opens seventy-two hours before arrival, so it cannot be done weeks ahead, and it asks for your passport, your flight and your first night's address. Only travellers transiting without clearing immigration, or entering on a border pass, are excepted. It is free on the Thai Immigration Bureau's own site, and paid look-alike sites are worth avoiding.
Do I need a new arrival card if I leave Thailand and come back?
Yes. The card is filed per entry, so a few days in Laos, Cambodia or Malaysia in the middle of your trip means completing another one before you cross back in. It is a good argument for a regional plan rather than a Thailand-only one on any itinerary with a border hop: the day you re-enter is a day you want a working connection, not a day to discover your plan stopped at the frontier.
Will my eSIM work the moment I land at Suvarnabhumi?
If you installed it before flying, yes. Install at home over wifi and leave the line switched off; nothing starts counting until it first connects to a Thai network. When you land, switch the line on, turn on data roaming for it, and it registers within a minute or two — usually before you reach immigration. Installing after landing is possible but depends on airport wifi, which is the exact dependency you were trying to avoid.
Which Thai network will my eSIM use?
AIS or True, which between them carry almost the entire Thai market and both run 5G across Bangkok, the main islands and the northern cities. True absorbed dtac in 2023, so seeing both names in your phone's network list is normal. Your phone picks the strongest available network by itself; the manual list is only worth opening if data has gone sluggish somewhere more than one network reaches.
Do I get a Thai phone number with a travel eSIM?
No. A travel eSIM is a data plan, so there is no Thai number attached and no local calls or texts from it. Anything that insists on a Thai number will not work through it. Your own number stays live on your home SIM alongside the eSIM, so codes from your bank and your usual apps still reach you, which is generally what people actually need while travelling.
Do I have to register my passport to use an eSIM in Thailand?
No. Registration applies to Thai SIM cards: buying a local prepaid SIM means handing your passport across a counter to be photographed and registered against the number, and those identity checks have been tightening rather than loosening. A travel eSIM connects as a visiting line rather than a Thai subscription, so there is no counter, no photocopy and no form. The trade-off is that there is no Thai number at the end of it either.
Is unlimited data worth it in Thailand?
Usually not. Thailand's fixed plans are cheap enough that a week of unlimited costs about three fifths more than a whole twenty-gigabyte month, which runs four times as long. Unlimited only becomes the right buy above roughly a gigabyte and a half of use a day, sustained — someone working remotely, tethering a laptop through the day, uploading video every evening. For an ordinary holiday it is the most expensive way to buy less data than you expected.
How long does a Thailand eSIM last before it expires?
There are two clocks. The plan's own window — thirty days for most Thailand rows, ten for the large short-window plan, one hundred and eighty for the long one — starts when the eSIM first connects to a Thai network, not when you buy it. Before that, an uninstalled and unconnected eSIM keeps for months, which is why buying weeks ahead of a trip is safe. Buy within five months of travelling and you have plenty of margin.
Will I have data on the ferry to the islands?
Close to shore, usually. In open water between islands, often not, and on smaller long-tail boats you should assume not. Ferry routes pass out of reach of land masts for long stretches and no plan or seller changes that. Download offline maps and screenshot your boat times and pier names before you board rather than planning to reload them halfway across.
Can I use one eSIM for Thailand and Vietnam?
Yes, on the seven-country Southeast Asia list, which covers Cambodia, Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam. For that pair it is also the cheaper buy: Vietnam alone costs roughly double a Thailand plan, so the regional list beats two country plans from the moment Vietnam is on the route. A Thailand-only plan stops working the moment you cross the border.
Can I use a Thailand eSIM for a one-month stay?
Yes. Most Thailand rows run thirty days, so a month in one place is well inside range — the twenty-gigabyte month suits most people, and you can top up mid-stay if you run through it, with the new days added to what is left rather than replacing it. Beyond about a month it gets less clear-cut, and past two or three months a local prepaid package is usually cheaper.
What happens if I use all my data before the trip ends?
Nothing is charged and nothing else is cut off. The data stops, the eSIM stays installed, and you add more from your account — a top-up refills the profile already on your phone, so do not delete it. Two Thailand rows cannot be topped up and carry a No top-ups badge on the plan card: the single-day plan and the large ten-day one. On those, more data means a second eSIM rather than a refill.