Island coverage in Thailand and how much data

Thailand is the backpacking destination and, as it happens, one of the best-covered countries in Asia for mobile data. The network is not the problem — the problem is connecting to it without your home carrier charging you for the trip twice. Here are the options, where the signal genuinely disappears, which apps locals use, and how much data to buy for the way you travel.

Getting online in Thailand

Roaming on your home plan

Thailand sits in the most expensive zone of almost every foreign tariff: daily bundles with a few hundred megabytes, or per-megabyte billing. A week of maps and photos on per-megabyte rates can run into the hundreds. Unless your tariff has a travel add-on you already know and trust, rule it out.

A tourist SIM at the airport

Suvarnabhumi and Don Mueang both have operator counters selling tourist SIMs valid 8, 15 or 30 days for a few hundred baht. It is a solid, cheap option. The catches: queueing with your passport after ten hours in the air (registration is compulsory), keeping your home SIM safe, and a fixed duration that rarely matches your trip exactly. 7-Eleven stores sell SIMs too, with the same registration.

A travel eSIM

You buy the days you need, install the QR on wifi at home, and land connected to a Thai network. Your home SIM stays in the phone with its data off, ready to receive calls or verification texts. For most one-to-four-week trips it is the easiest choice, and if you are carrying on to Laos or Cambodia you can take a regional plan that works in all of them.

Real coverage: networks and where it fails

Two big networks: AIS and True (which absorbed dtac in 2023). Both comfortably cover Bangkok, Chiang Mai, Chiang Rai, Ayutthaya, Sukhothai, Phuket, Krabi, Koh Samui and Pattaya, with fast 4G and 5G in the cities. AIS has the reputation for reaching a little further into the rural north; True is very strong in Bangkok and the south.

Where the signal suffers, whichever network you are on:

• Mountain roads in the north (Pai, Mae Hong Son, the Mae Hong Son loop by motorbike): long stretches with nothing between villages.
• Inland on the big islands and the remote coves of Koh Phangan, Koh Tao or Koh Lanta: 4G in the village and on the main beach, nothing in the hidden bay.
• Ferries and speedboats between islands: gone a few minutes after leaving the pier.
• National parks (Khao Sok, Khao Yai): fine at the entrance and the lodges, hit and miss on the trails.
• The slow boat to Laos down the Mekong: two days with almost no signal, and the Thai eSIM stops working the moment you cross the border.

Worth saying plainly: the eSIM runs on the AIS or True network, not on one of its own. Where their masts do not reach, no eSIM will help — not ours, not any provider’s. What you can do is arrive prepared: maps downloaded and your accommodation warned.

A trick from people who have been there: if your plan can use more than one network and you get nothing in a particular spot, go into the eSIM’s settings → Network selection and pick the other operator by hand.

How much data you need

Thailand is a Grab, maps, translate and lots of photos destination, with decent wifi in hostels and cafés. What drives the numbers up is posting video from every beach and watching things on long bus journeys.

Kind of trip	Typical use	Plan that fits
Maps, Grab, messages, the odd photo	300-500 MB a day	5 GB for one or two weeks
The above plus daily social media and stories	700 MB - 1 GB a day	10 GB for two weeks, or unlimited
Video, video calls, working off a laptop	Over 1.5 GB a day	Unlimited by the day

A month of backpacking with normal use usually lands at 15-20 GB. Per-app figures are in the Spanish guide ¿Cuántos GB necesito para viajar?.

Installing the eSIM and landing connected

1. Compatibility: dial *#06# and look for the EID. Carrier-unlocked phone. The list by brand is on the compatibility page.
2. Buy your travel dates: validity starts with the first connection in Thailand, not at purchase.
3. Install at home on wifi: iPhone → Settings → Mobile Data → Add eSIM; Android → Settings → Connections → SIM manager → Add eSIM. Name it “Thailand”.
4. Lines: home SIM for calls and texts with data off; eSIM as the mobile data line with roaming on.
5. On landing: turn off airplane mode; within seconds you should see “AIS” or “TRUE-H”. If not, toggle airplane mode, and if it still will not connect, go back to step 4.

The detail of every menu is in What is an eSIM and how does it work?.

Apps locals use (and you will too)

• Grab: cars, motorbike taxis and food delivery at a fixed price. It saves you haggling with tuk-tuks and meterless taxis in Bangkok; Bolt also works in Chiang Mai and Phuket.
• Google Maps with the city downloaded, plus transit mode for Bangkok’s BTS and MRT.
• Google Translate with Thai downloaded: the camera reads menus and signs without data.
• 12Go: train, bus and ferry tickets between cities and islands, with real timetables.
• LINE: the Thai WhatsApp. Plenty of guesthouses and agencies answer nowhere else.
• Agoda: usually has more Southeast Asian stock and better prices than the alternatives.
• Paying: locals pay by QR (PromptPay), which needs a Thai bank account. You will use a card in bigger places and cash at stalls, markets and taxis. ATMs charge a flat fee per withdrawal, so take out more, less often.

Connectivity tips

• Message your accommodation on LINE or WhatsApp with your arrival time before you leave a covered area.
• Download before the ferry: the island map, the hostel voucher, the next episode.
• Motorbikes and the Mae Hong Son loop: offline map and your route shared with someone. Long sections have no signal from anyone.
• Hostel and café wifi: great for uploading and downloading; for banking, use mobile data.
• Calling home: WhatsApp, always. The eSIM is data only and your home line charges for calls.
• Multiple countries: if the trip continues to Laos, Cambodia, Vietnam or Malaysia, look at a regional Asia plan before buying a local one.

What it costs

The price block at the top of this guide shows what a Thailand eSIM costs in the MovaSim catalogue today: the unlimited-by-day option and the cheapest per-GB one. Every plan, with the countries it covers, is on the Thailand page. The advice above works just as well with any eSIM, or with the SIM you buy at the airport.