Thailand is easy to travel and hard to read. The coverage is better than most visitors expect, the transport is cheap and frequent, and absolutely none of the signage will make sense to you without help. Data in Thailand is less about staying reachable than about being able to function.
The script problem
Thai uses its own script, and outside the most touristed streets you will encounter menus, bus destinations, price boards, medicine packets and street signs written entirely in it. There is no guessing your way through it the way you might with Italian or Spanish.
The translation camera is the single most useful thing on your phone here. Point it at a menu and it renders in English; point it at a pharmacy box and you learn what you are about to take. It needs a connection to work properly, which is the practical argument for having data in the market rather than back at the hotel.
What coverage is honestly like
Urban and resort coverage is genuinely good. Bangkok has dense 4G and widespread 5G including on the BTS Skytrain and the MRT underground. Chiang Mai, Phuket, Krabi, Ao Nang, Hua Hin and Pattaya are all well covered, as are the main towns and beaches of Koh Samui, Koh Phangan and Koh Tao.
It thins in the interiors and the mountains. The Mae Hong Son loop north of Chiang Mai has stretches with nothing, as does much of Khao Sok and the other inland national parks. Island interiors — the jungle roads across Koh Samui or Koh Chang — drop out between the coastal towns.
Boats are the real gap
This is the one that catches people. Ferry and speedboat crossings between the mainland and the islands, and between islands, lose signal in the middle. The run out to Koh Phi Phi, the Surat Thani crossings to the Samui archipelago, the boats to Koh Lipe — all of them have a long middle section with nothing at all.
That matters more than it sounds because island transfers are exactly when plans change. Screenshot your ferry ticket and your onward transfer, save your accommodation as a pin, and confirm your pickup before you board rather than assuming you can sort it on the water.
Ferry schedules also shift with weather, particularly in monsoon season, and operators announce changes on their own channels first. Checking before you travel to the pier saves a wasted morning.
The networks you will connect to
AIS has the widest national reach and is usually what still works in rural and island areas. TrueMove H, now merged with dtac, is the other major network and is strong in the cities and resort zones. A travel eSIM roams onto whichever partner network is strongest where you are standing.
Getting around, and why Grab matters
Grab is the dominant ride-hailing app in Thailand and it changes the experience considerably. It fixes the fare in advance, removes the negotiation, and means you are not standing at a taxi rank as an obvious visitor working out whether the meter is running. It needs data to hail, track and pay.
If you are renting a scooter — which a great many visitors do on the islands — navigation becomes the thing you rely on most, and the island roads are exactly where coverage is thinnest. Download the offline map of every island you plan to ride around.
The Bangkok airport trap
Bangkok has two airports: Suvarnabhumi, which handles most international flights, and Don Mueang, which handles most domestic low-cost carriers. They are on opposite sides of the city and a transfer between them can take well over an hour, considerably more in Bangkok traffic.
People book a cheap domestic flight to the islands without noticing it leaves from the other airport. Check which airport each leg uses, and on the day watch live traffic rather than a static estimate.
How much data you will actually use
Plan on 5 to 7 GB for a week, which is higher than a European city trip. The translation camera is a constant draw, navigation runs while you ride, and Thailand generates an enormous number of photos and videos.
Longer trips are common here — two weeks, a month, a winter — and at that length unlimited is usually the sensible answer. Turn off automatic cloud photo backup over cellular before you fly.
Who this suits
First-time visitors doing Bangkok and the islands, who will need the translation camera constantly. Island hoppers taking boats, where the gaps are real. Anyone renting a scooter. Travellers connecting through Bangkok's two airports. Long-stay visitors and remote workers in Chiang Mai. And anyone who has looked at a Thai bus timetable and understood nothing on it.
Temples, etiquette and looking things up
Thailand has rules about temples that are taken seriously and are not always posted in English: covered shoulders and knees, shoes off, no pointing your feet at a Buddha image, and restrictions that vary between sites. The Grand Palace in Bangkok turns people away daily for dress, and it is a long trip to make twice.
Being able to check the specific requirements of the specific temple before you set out — rather than after you have queued — saves the wasted journey. The same goes for opening hours, which shift around Buddhist holidays in ways that are not always advertised where a visitor would see them.
Timing your plan to the trip
Thai trips run long by Canadian standards, and often loosely — people extend, add an island, stay another week. Pick a plan with room in it rather than one that expires precisely when your original itinerary said it would, because the itinerary is the thing most likely to change.
Install at home on Wi-Fi before you fly. The profile stays dormant until it first connects to a Thai network, so a long flight with a stopover does not eat into it.
Frequently asked questions
Will I have signal on the ferry to the islands?
Not in the middle of the crossing. Coverage holds near shore and disappears offshore, on every route. Screenshot your tickets and confirm your onward transfer before you board.
How much data do I need for two weeks in Thailand?
More than a European trip of the same length — plan on 10 GB or more, or go unlimited. The translation camera, scooter navigation and heavy photo sharing all add up faster here.
Do I need data to read menus and signs?
Effectively yes. Thai script is not something you can work out by context, and the translation camera needs a connection to work well. It is the most-used feature on most visitors' phones here.
Which Bangkok airport does my flight use?
Check when booking — Suvarnabhumi handles most international flights and Don Mueang most domestic budget carriers. They are on opposite sides of the city and transferring between them takes well over an hour in traffic.