A Thailand eSIM starting at £2.49 keeps you online across the main island destinations - Phuket, Koh Samui, Koh Phi Phi and Krabi - but no eSIM and no network gives you full signal on the smaller islands, the ferries between them, or the quiet beaches at the far end of the archipelago. That is the honest picture, and this guide walks through exactly where your phone will work, where it will not, and how to prepare so a dead zone never leaves you stranded.
Island hopping is the best part of a Thailand trip and also the part that tests your connectivity the hardest. You are constantly moving between land and water, between busy resort bays and empty coves, and coverage moves with you. Understanding that pattern before you sail beats discovering it mid-crossing with a booking to confirm and no bars on the screen.
Thailand eSIM Plans and Pricing
| Data | Duration | Price |
|---|---|---|
| 1GB Data | 7 Days | £2.49 |
| 3GB Data | 30 Days | £3.17 |
| 5GB Data | 30 Days | £4.68 |
| 10GB Data | 30 Days | £7.40 |
| 20GB Data | 30 Days | £11.33 |
| 1 Day | 1 Day | £2.59 |
| 2 Days | 2 Days | £5.19 |
| 3 Days | 3 Days | £7.78 |
| 4 Days | 4 Days | £10.20 |
| 5 Days | 5 Days | £12.93 |
| 6 Days | 6 Days | £15.67 |
| 7 Days | 7 Days | £18.41 |
| 8 Days | 8 Days | £19.78 |
| 9 Days | 9 Days | £21.83 |
| 10 Days | 10 Days | £23.20 |
| 11 Days | 11 Days | £25.25 |
| 12 Days | 12 Days | £27.30 |
| 13 Days | 13 Days | £28.67 |
| 14 Days | 14 Days | £30.04 |
| 15 Days | 15 Days | £32.09 |
| 16 Days | 16 Days | £33.46 |
| 17 Days | 17 Days | £34.15 |
| 18 Days | 18 Days | £35.51 |
| 19 Days | 19 Days | £37.57 |
| 20 Days | 20 Days | £38.94 |
| 21 Days | 21 Days | £40.30 |
| 22 Days | 22 Days | £40.99 |
| 23 Days | 23 Days | £41.67 |
| 24 Days | 24 Days | £42.36 |
| 25 Days | 25 Days | £43.04 |
| 26 Days | 26 Days | £43.73 |
| 27 Days | 27 Days | £44.41 |
| 28 Days | 28 Days | £45.09 |
| 29 Days | 29 Days | £45.78 |
| 30 Days | 30 Days | £47.15 |
A Thailand eSIM connects to a major local network in the country, so on land you get the same towers a Thai phone uses. Coverage follows those towers. Where the network built masts - the developed islands and the mainland coast - you are online. Where it did not - remote outer islands and open water - nobody is, regardless of which plan or provider you bought.
Where Coverage Is Solid
The big, developed islands have real infrastructure and generally reliable 4G, with 5G appearing in the busiest areas:
- Phuket: The most connected island in the country. Solid coverage across Patong, Kata, Karon, Old Town, the airport and most beaches. Treat it like a mainland city.
- Koh Samui: Strong coverage around Chaweng, Lamai, Bophut and the ring road. Fine for maps, Grab, streaming and calls.
- Koh Phi Phi: Good signal around Tonsai village, the pier and the main resort strip. It fades on the viewpoint trails and the quieter back bays.
- Krabi and Ao Nang: The mainland hub for the Andaman islands is well covered, including Ao Nang beach and the Krabi town area. Railay, just around the headland, has usable coverage near the resorts.
- Koh Lanta: Reliable along the main west-coast beaches and the primary road.
On these islands your eSIM behaves exactly as it does in Bangkok. If your itinerary sticks to them, you will barely notice you left the mainland.
Where Coverage Gets Patchy or Disappears
This is the section most connectivity guides skip. Being honest about it is what keeps you out of trouble:
- Small outer islands: Koh Kood (Koh Kut) far in the east has thin and inconsistent coverage away from the larger resorts. The Similan Islands, a marine national park, are effectively offline - there is little to no mobile signal, and day-trip boats leave you disconnected for hours. Parts of Koh Tao away from Sairee Beach and the main dive village can drop out.
- Ferries and longtail boats: Once you are a few kilometres offshore, you lose land towers and signal goes with them. Speedboat transfers, longtail hops and the longer ferry crossings (Krabi to Phi Phi, Surat Thani to Samui, mainland to Koh Tao) spend long stretches with no usable data. You may catch a bar or two near either shore and nothing in the middle.
- Remote beaches and headlands: Even on a well-covered island, a cove tucked behind a hill or a beach at the undeveloped end can sit in a shadow with no signal. Limestone cliffs block reception the same way buildings do.
- National marine parks: Ang Thong, the Similans and Surin are protected and largely undeveloped, which is wonderful for the scenery and unfortunate for your bars.
No network fully fixes this. Of the local networks, AIS has the widest reach onto smaller and more remote islands, so a travel eSIM that rides on AIS tends to hold signal in more places than one that does not. But "widest" is not "everywhere," and you should still plan for gaps rather than assume them away.
How to Prepare for the Dead Zones
The fix is not a better SIM. It is a bit of preparation before you leave signal:
- Download offline maps. In Google Maps, save the islands and coastline you will visit for offline use. GPS positioning works with no signal at all, so your blue dot keeps moving and navigation keeps running even mid-crossing.
- Cache your bookings. Screenshot or download ferry tickets, hotel confirmations, the address in Thai script, and your host's phone or LINE contact. If you cannot load the email at the pier, the screenshot still opens.
- Message home before you sail. Tell someone your boat, your destination and your rough arrival time before you push off. A short "heading to Koh Kood, back online tonight" saves worry when you drop off the grid for a few hours.
- Download entertainment for the crossing. Music, podcasts and shows saved offline turn a two-hour dead-zone ferry into an easy ride.
- Know your next pickup point. Cache where your transfer meets you and what the boat or driver looks like, so a no-signal arrival is not a problem.
Do these five things and the gaps stop mattering. You stay functional offline and pick your connection back up the moment you reach a covered bay.
How Much Data Island Hopping Uses
Island days are often lighter on data than city days - you are on the beach, not scrolling - but transfers and evenings add up:
- Light use (maps, messaging, the odd photo upload): 1-2 GB per week
- Moderate use (add social media, video calls home, some streaming): 3-5 GB per week
- Heavy use (daily video calls, hotspot for a laptop, lots of streaming): 7-10 GB per week
Get a personalised estimate for your trip:
Because so much of an island itinerary happens offline on boats and beaches, most hoppers land in the light-to-moderate range and a mid-size plan lasts the whole trip.
Why a Thailand eSIM Still Wins for Islands
Coverage gaps are geography, not a fault of the eSIM. Where signal exists, a Thailand eSIM is the easiest way to use it:
- No airport SIM queue, no passport counter. Thailand requires passport registration to buy a physical tourist SIM. An eSIM bought online skips the registration desk entirely - you scan a QR code and you are set before you even land.
- Installed before you fly. You add the eSIM at home over Wi-Fi, then it activates when you reach Thailand. No hunting for a shop on arrival, no swapping a tiny card on a rocking boat.
- Your home number stays live. The plan is data only, so your regular SIM keeps your number for calls and texts while the eSIM carries the data. WhatsApp, LINE, Telegram and Grab all run over it.
- Cheaper than roaming. Home-network roaming in Thailand runs steep per-GB or per-day rates. An eSIM avoids that. If you are weighing the two, our eSIM vs roaming breakdown lays out the difference.
For the full rundown on plans, coverage and picking a size, see our guide to the best eSIM for Thailand. When your eSIM arrives, the eSIM installation and activation walkthrough gets you connected in a couple of minutes.
eSIM vs Roaming vs Local SIM for Island Trips
eSIM vs Roaming vs Local SIM
Compare your options for Thailand
| eSIMpass | Roaming | Local SIM | |
|---|---|---|---|
| Setup time | Instant | None | 30-60 min |
| Cost per GB | ~$2-5 | $10-50+ | ~$3-8 |
| Surprise fees | None | Likely | Unlikely |
| Buy before trip | Yes | Yes | No |
| Keep your number | Yes | Yes | No |
| Speed | 4G/5G | 4G/5G | 4G/5G |
A physical local SIM means the passport-registration counter and swapping cards on the move, which is awkward when your day is a chain of boat transfers. Roaming works without setup but costs far more per GB. The eSIM sits in the middle for effort and lowest for cost: installed once at home, active the whole trip, and priced for how little data an island week actually uses.
Get Your Thailand eSIM Before You Sail
Set it up before you leave, cache your maps and bookings, and you will be connected on every island that has a signal - and calmly offline, by choice, on the boats and beaches that do not.
Ready to island hop without hunting for a SIM shop?
A Thailand eSIM covers Phuket, Samui, Phi Phi and Krabi with instant QR delivery. Install it at home and activate the moment you land.
Get Your Thailand eSIMFrequently Asked Questions
Does a Thailand eSIM work on the islands?
On the developed islands, yes. Phuket, Koh Samui, Koh Phi Phi, Krabi, Ao Nang and Koh Lanta have solid 4G, and you will be online across their main areas. Small outer islands like Koh Kood, the Similans and quieter parts of Koh Tao have thin or no coverage, and no provider fully fixes that.
Will I have signal on the ferry between islands?
Usually not for the whole crossing. You lose land towers a few kilometres offshore, so speedboat, longtail and ferry transfers spend long stretches with no data. Download offline maps and your bookings before you board and treat the crossing as offline time.
Which network reaches the most islands?
Among Thailand's local networks, AIS generally has the widest reach onto smaller and remote islands, so an eSIM riding on AIS tends to hold signal in more places. It still is not everywhere, so plan for gaps rather than counting on full coverage.
Do I need to register my passport for an eSIM like I do for a SIM card?
No. Thailand requires passport registration to buy a physical tourist SIM at a counter, but an eSIM bought online skips that entirely. You scan a QR code and connect - no desk, no paperwork.
How do I stay safe when I lose signal between islands?
Message someone your boat and destination before you sail, cache your ferry and hotel details, and save offline maps so navigation keeps working. GPS runs with no signal, so your position still updates even mid-crossing. Reconnect the moment you reach a covered bay.
How much data should I buy for an island-hopping trip?
Most island trips are lighter on data than city trips because so much of the day is offline on beaches and boats. A 3-5 GB plan comfortably covers a week of maps, messaging, social media and the occasional video call for a moderate user.
