Journal ·
Koh Phangan SIM Cards, eSIMs and Where the Signal Drops
Which Thai network to choose, why the airport counter costs more, when an eSIM beats a local number, and the parts of Koh Phangan where coverage fails.
Staying Connected on Koh Phangan: SIMs, eSIMs and Where the Signal Drops
Most people arrive on Koh Phangan with a plan for the ferry and no plan at all for their phone. Then they land, find the villa's gate code is in an email, and discover roaming is costing more per day than lunch for four. This is the boring half-hour of admin that makes the rest of the trip easier, so here it is in one place.
Three networks, two of them now related
Thailand has AIS and True, and dtac — which merged into True Corporation and still appears under its own branding on some packages. For practical purposes you are choosing between two networks with two shopfronts.
The received wisdom is that AIS holds up slightly better in rural and remote areas, while True is strong in cities and tourist areas. On Koh Phangan specifically, True has made a visible push: in August 2026 it expanded 5G coverage across the island and along the travel route from Surat Thani airport to the pier and over the ferry crossing. Both networks work for a normal holiday here. If you are choosing blind, AIS is the safer default for the island's interior; True is a good bet if the package suits you better.
One honest caveat: five bars of 5G is not the same as fast internet. Even on full signal, video apps buffer at busy hours, and Koh Phangan has a lot of people doing video calls at once in high season.
Buying when you land: the airport costs more
Tourist SIMs sold at airport counters are the expensive version of the same thing. Through 2026, unlimited 30-day tourist packages at airport kiosks have typically run around 999–1,199 baht, while the equivalent AIS tourist packages bought in town or at 7-Eleven have been more like 299 baht for 15 GB over eight days, around 599 baht for 30 GB over fifteen days, and around 899 baht for 50 GB over thirty days. AIS has also sold a one-day 1 GB SIM for about 49 baht, which is enough to get you through an arrival day.
Prices change, promotions change, and the counter staff will push the biggest package. Decide your rough data need before you walk up.
You will need your passport. Registration at point of sale is a legal requirement in Thailand, and the shop assistant will do it for you — it takes a few minutes, and recent rules have tightened identity checks, so expect to be photographed or face-scanned in some shops. Topping up afterwards is easy: any 7-Eleven, and there are plenty in Thong Sala.
If you would rather not queue at Samui airport with your luggage, you can wait. There are phone shops and 7-Elevens in Thong Sala, ten minutes from most of the island's interior, and the ferry crossing itself is short.
eSIM: usually the tidiest option
If your phone supports eSIM, buying one before you fly removes the whole errand. Two different things get sold as "Thailand eSIM":
- Operator eSIMs from AIS or True, which give you a Thai number and run on the networks directly.
- Travel eSIMs from international resellers, which roam onto Thai networks. Cheap ones have started around US$10 for roughly 10 GB over 30 days.
The trade-off is the phone number. Most travel eSIMs are data-only, so you cannot receive Thai SMS. That matters more than people expect: food delivery apps, ride apps and some bookings send one-time codes to a local number, and a boat driver who needs to call you back cannot. If you plan to use delivery and taxi apps a lot, get a Thai number.
The other advantage of eSIM is that your home SIM stays in the phone, so bank verification codes keep arriving. Set your home line to data off, keep it for SMS only, and run everything else over the eSIM.
Where the signal actually goes
Koh Phangan's coverage is good on the ring road, strong in Thong Sala, Baan Tai, Srithanu and Chaloklum, and reliable at the main beaches. The gaps are structural rather than random, and they follow the terrain:
- Steep interior roads between the west coast and the north-east, where granite ridges sit between you and the nearest mast.
- The far east and north-east — the tracks towards Than Sadet and the walk-in beaches — where a dead phone and a dead signal at once is a genuine problem.
- Beach-level spots with a hill directly behind them, which can be weaker than a hilltop two kilometres inland with an open aspect.
Before you ride anywhere off the ring road, download the island in Google Maps for offline use. It is a thirty-second job and it is the difference between a wrong turn and an hour of wrong turns. Tell someone where you are going if you are riding alone to the east side.
Two more island realities worth knowing. Mobile data is often the thing that still works when the village power goes out, so a charged phone with a local SIM is a sensible backup — we have written separately about how power cuts work here. And villa or hotel wifi is only as good as its uplink; if your week depends on calls, carry your own data as a fallback rather than assuming.
A short checklist
- Passport in hand when buying a SIM, not in the safe.
- Buy in town rather than at the airport counter if you can wait an hour.
- eSIM for data, home SIM in the phone for bank codes.
- A Thai number if you want delivery and ride-hailing apps to work properly.
- Offline maps downloaded before you leave the pier.
At Villa Ullassa we are on a ridge above Maduawan with an open west aspect, which tends to be a kinder place for a phone than a beach hemmed in by hills — but the island's rule holds everywhere here: the signal belongs to the terrain, not to the postcode. Sort your data out on day one, then put the phone down for the rest of the week.
Villa Ullassa is a private four-bedroom house on a jungle hillside above Maduawan, with a 180° sunset sea view, a saltwater pool and room for eight.