soda Journal
Best eSIM for Thailand: the complete guide
A Thailand trip usually spans very different places: shopping in Bangkok, the hills around Chiang Mai, island-hopping down south. Whether your connection holds up depends very little on central Bangkok, where signal is everywhere, and almost entirely on what happens once you leave it. That’s the part this guide is really about.
First, what Thai mobile coverage is like
Thailand has three big carriers, AIS, True, and dtac, and across cities like Bangkok, Chiang Mai, and Phuket they all do the job. Speeds are fine for navigation, video, and calls, so in town it barely matters which one your eSIM runs on. The thing that actually varies is the islands and the remote stretches. Put another way, the question in Thailand isn’t “which carrier is best,” it’s “are you going somewhere nobody has built a cell tower?”
Bangkok: much like any big city
Good signal downtown and plenty of Wi-Fi. Navigation, booking a Grab, checking restaurants, sending photos: 0.8 to 1.5GB a day is plenty (illustrative figures; your own use depends on how heavy you are). To size your own day, the behaviour-by-behaviour table in how much data do you need does the work.
One quiet drain worth knowing about: Bangkok traffic is famous, and a Grab stuck in it means your maps stay open and your messages keep flowing the whole time. That adds up, but it’s still comfortably inside “plenty.” The part to actually plan for is below.
Leaving the city is the real question
- Island-hopping (Phuket, Samui, the Phi Phi islands): signal weakens the moment the boat leaves the pier, and out in open water it often disappears completely.
- Chiang Mai hills, long night buses: mountain roads wind in and out of coverage and navigation can freeze on you.
- Grab, food delivery, QR payments: used constantly in Thailand, and every one of them needs a live connection at that exact moment, which tends to be while you’re moving and the signal is shaky.
So in Thailand the real question isn’t “how big,” it’s “how stable.” A card on a proper line that holds its signal a little longer beats a cheap one that drops the moment you leave town.
Where signal holds and where it drops, at a glance
The gap between places is huge, so before you go it helps to match your itinerary against the kinds of spots below (illustrative; actual signal depends on weather, crowds, and the carrier’s coverage where you are):
| Where you are | Signal | What to do |
|---|---|---|
| Bangkok, Chiang Mai, Phuket town | Steady, fast enough | Just use it normally, no prep needed |
| Big malls, night markets, attractions | Slows when crowded | Avoid sending big files at peak; upload photos back at the hotel |
| Boat crossings (open water) | Often none at all | Download offline maps, screenshot the ferry times first |
| Chiang Mai hills, night buses | In and out | Set navigation before you leave; save bookings offline |
| National parks, deep trails | Usually nothing | Plan as if offline; keep paper or screenshots |
Notice the pattern: the trouble is almost always “once you leave the concrete city.” In town everything just works, so when choosing a card, instead of agonising over gigabytes, first make sure it holds on a little longer out in the remote spots.
Why signal dies on a boat or up a mountain
In plain terms, your phone’s data comes from towers planted on the ground. The farther you are from a tower the weaker the signal gets, and past a certain distance you get nothing at all. In a city the towers are packed close together, so you’re always connected. But once a boat reaches open water, there’s nothing but sea around you and nowhere to put a tower, so the signal simply runs out. Mountains are similar: fewer towers, and the hills themselves block the radio waves, so one bend in the road can cut you off.
None of this has anything to do with which eSIM you bought or how many gigabytes are on it. All the data in the world can’t connect you when there’s no signal to ride on. If it helps to separate “signal” from “eSIM” in your head, eSIM vs SIM card explained walks through why the two are different things.
What to set up before you go
Since some stretches are guaranteed to drop, the smart move is to save what you’ll need offline so a dead zone doesn’t strand you:
- Offline maps: in Google Maps, download the whole Phuket or Samui area ahead of time so you can locate yourself and navigate with no signal.
- Ferry and transfer times: screenshot the boat schedule and pier details rather than planning to look them up on the spot.
- Bookings: save your hotel address, reservation number, and check-in notes to your photos or notes app.
- Key messages: keep the contact details and arrangements with your boat operator or guesthouse where you can reach them offline.
Do that and the hour or two at sea without signal stops being a problem; you already know your next move.
Walking through a real Phuket island day
Run through a typical island-hopping day and the issue becomes obvious. In the morning you check out of your Phuket hotel and grab a ride to the pier; signal is fine the whole way, the Grab arrives, the map flows. Step onto the speedboat and the bars start flickering, and maybe fifteen minutes later, out in open water, the phone simply has no signal. That’s exactly when you might want to look up the next snorkel spot or what time the return boat leaves, and you can’t.
So the people who never get caught out did their saving back at the hotel, on Wi-Fi: the day’s boat times, landing slots, and return transfer all screenshotted, the offline map already downloaded. Then the stretch at sea with no signal bothers them not at all, because everything they need is sitting in their camera roll. The point isn’t how much data you used that day (it’s very little); it’s whether you prepared for the gap.
Why a big data cap is the wrong thing to chase here
A lot of people pick a card by asking “how many GB is the best deal,” but in Thailand that’s backwards. When you’re in the city with good signal, you have plenty of data anyway; the thing that actually leaves you stuck is the no-signal gap on the islands and in the hills, and 100GB wouldn’t save you there. So get a stable line with good city coverage first, make sure the data is merely enough, and don’t obsess over buying a huge bundle. For why pricing by amount spent beats counting gigabytes, see how much data do you need.
How soda works in Thailand
soda runs on Thailand’s proper carrier lines, with stability set as the floor rather than an afterthought, and you feel that most on the boat and up in the hills. You also don’t pre-pick how many GB for Thailand. You land, open it, and we bill by actual usage, capped at the cheapest plan price. On the island days when signal is weak and you barely use anything, you pay barely anything, and nothing is left over to waste because you never bought a bundle in the first place.
Honestly, soda isn’t always the cheapest, but you never lose: you pay for what you use, the balance never expires, and the line is steady. Pairing Thailand with a neighbouring country? See one eSIM for a multi-country trip.
Common questions
Will I have internet while island-hopping in Thailand? Near the islands and the shore you usually do, but the stretch when the speedboat is out in open water is mostly a dead zone. No card fixes this, because there are no towers at sea. The answer is to save your ferry times, maps, and bookings offline before you set off.
eSIM, a physical SIM, or a pocket Wi-Fi for Thailand, which is best? For one or two travellers an eSIM is the easiest: land, scan, done, with no card to swap and no device to deposit. A pocket Wi-Fi only makes sense for a big group, and even then it loses signal at sea just the same, which has nothing to do with the card.
Do Grab and QR payments need a connection? What if I have no signal? Yes. Booking a ride and paying both need a live connection at that moment, which is exactly why a stable line matters more than a big cap. Carry some cash for the dead zones and don’t pin every payment on one method.
Is the signal bad going to the Chiang Mai hills or on a night bus? In-and-out coverage on mountain roads is normal, so don’t panic when navigation freezes for a bit. Set your destination and download the offline map before you leave, and you’ll still roughly know where you are when the bus has no signal.
Do I need separate cards for northern and southern Thailand? No. As long as the plan covers all of Thailand, Bangkok, Chiang Mai, Phuket, and Samui all count as domestic on one card. With soda it’s simpler still: no regions to pick, billed by actual usage, so crossing between cities is something you never even notice.