Do eSIMs Work on Thailand's Islands?
Yes, eSIMs work well in tourist areas on Thailand's islands, with strong coverage on major islands like Phuket and Koh Samui. Coverage thins in island interiors, on overnight ferries mid-crossing, and on the smallest and most remote islands. The key is choosing the right network and downloading essentials before each boat trip.
As of 2026, Thailand's mobile market has consolidated into an AIS and True Move H (TrueMove H) effective duopoly following the DTAC-True merger in 2023. For island travel specifically, AIS has measurably better coverage outside main tourist zones, including rural island interiors and smaller islands where True's infrastructure is thinner. Our Thailand eSIM uses leading Thai 5G networks (AIS / TrueMove H); see the live network on our Thailand destination page.
Island-by-Island Coverage Guide
Phuket, Strong 5G Throughout Tourist Areas
Excellent coverage across all major tourist zones: Patong Beach (5G in the central Bangla Road and Jungceylon area), Kata and Karon, Rawai, and Phuket Town. The east coast ring road maintains strong 4G. Phuket International Airport has excellent coverage. No meaningful issues for Grab, Google Maps, Instagram, or video calls in tourist areas.
Patchy areas: Remote interior roads and forests in Khao Phra Thaeo National Park have reduced signal. Download offline maps before heading inland.
Koh Samui, Good 4G East Coast, Weaker West and Interior
Strong 4G (occasional 5G) along the east coast tourist strip: Chaweng, Lamai, Bophut Fisherman's Village, and the Nathon ferry pier. Coverage weakens along the quieter west and south coasts and in the hilly interior.
Before leaving Chaweng: Download offline maps for the entire island, including the Ring Road route to the airport.
Koh Phangan, Patchy Overall
Haad Rin (Full Moon Party area on the south coast) gets temporary signal reinforcement during major events; base coverage is adequate. Thong Nai Pan and Bottle Beach on the north coast are beautiful but weak signal zones. Interior mountain roads and waterfalls (Na Muang, Than Sadet) have limited or no coverage.
Recommended: Download offline maps for all Koh Phangan before taking the ferry from Koh Samui. Save your accommodation pin offline. AIS performs marginally better than True in Koh Phangan's coverage gaps.
Koh Tao, Decent at Main Beaches, Weak Elsewhere
Good signal at Sairee Beach (the main tourist strip), Mae Haad pier, and Chalok Baan Kao. Coverage weakens significantly on the east coast (Tanote Bay, Aow Leuk) and is minimal in the island interior. Dive sites underwater obviously have no signal.
Before the Lomprayah ferry: Download offline maps. Save your dive shop's WhatsApp contact, accommodation address, and the pier location offline. Koh Tao is small enough to navigate fully offline once you have the map downloaded.
Krabi Town and Ao Nang, Good Coverage
Krabi town, Ao Nang Beach, and Nopparat Thara all have solid 4G. The Ao Nang pier and boat taxi launch point are well-covered. Coverage holds along the main coast road.
Railay Beach, Inconsistent
Railay is accessible only by longtail boat from Ao Nang or Krabi town (8-15 minutes). Mobile signal reaches across the bay but is inconsistent, you may have one bar or nothing depending on conditions. The western beach (Railay West) has better signal than the eastern beach.
Before boarding the longtail: Download offline maps for Railay, confirm your accommodation address, and screenshot any booking confirmations. Do not rely on live Google Maps at Railay.
Koh Chang, Good in Town, Patchy Inland
Koh Chang is Thailand's second-largest island and has reasonable 4G coverage in White Sand Beach, Lonely Beach, and Ban Klong Prao. The east coast (less visited) and interior forest roads are patchy. The National Park areas have limited signal.
AIS advantage: AIS performs noticeably better than True on Koh Chang's less-frequented western coast and in the national park zones.
Koh Lipe, Main Beach Only
Koh Lipe in the far south Andaman Sea near the Malaysia border has signal at Walking Street and on the main beaches (Sunrise Beach, Pattaya Beach). Coverage is unreliable away from the main strip. Download everything before the Speedboat Link or Bundhaya Speed Boat crossing from Pak Bara.
Remote Andaman Islands (Surin, Similan, Phi Phi Don), Very Limited
Coverage at Phi Phi Don's Tonsai Bay is reasonable but inconsistent. Surin and Similan Islands are national marine parks with minimal or no coverage. These are offline destinations, download everything before the speedboat from Khao Lak or Chalong Pier.
Ferry and Overnight Boat Crossings: Signal During Transit
Signal behaviour on ferry crossings:
Short crossings (under 30 minutes, Krabi to Railay, Ko Lanta to Ao Nang): Signal fluctuates but generally maintains partial connection throughout.
Medium crossings (30-90 minutes, Chumphon to Koh Tao, Surat Thani to Koh Samui): Signal drops mid-crossing (roughly the middle third of the journey) and returns near the destination port.
Long/overnight crossings (8-14 hours, Bangkok to Koh Samui by Seatran ferry): Extended signal gaps, particularly in deeper Gulf of Thailand water. Download entertainment, offline maps, and all necessary contacts before boarding.
Practical rule: Treat every ferry departure as an opportunity to run through the offline prep checklist below.
Island Offline Prep Checklist (Before Every Ferry)
Run through this before each ferry boarding:
- Google Maps offline downloaded for the destination island
- Accommodation address and pin saved offline
- Ferry times for the return crossing saved offline
- Dive shop / tour operator WhatsApp contact saved to contacts list
- Restaurant or activity booking confirmation screenshots saved to camera roll
- Power bank charged (boats and beaches drain batteries)
- WhatsApp media auto-download set to "Wi-Fi only"
How Much Data for an Island Trip?
A typical island day (Grab on Phuket, offline Maps, Instagram, messaging) uses roughly 400-700 MB. A 10 GB plan comfortably covers a two-week island-hopping trip if you use accommodation Wi-Fi for large downloads and streaming. Heavy content creators uploading daily videos should step up to 15-20 GB or unlimited.
Frequently Asked Questions
Which network is best for Thai islands? AIS has the broadest rural and island coverage in Thailand, including a measurable edge on Koh Phangan, Koh Chang, and smaller islands where True coverage is thinner. In main tourist zones of large islands (Patong in Phuket, Chaweng in Koh Samui), both AIS and True perform similarly.
Will my eSIM work on Koh Tao or Koh Phangan? Yes, in the main beach and tourist areas. Interiors and secondary beaches on both islands have reduced or no signal. Download offline Maps and key contacts before the ferry.
Does eSIM work on ferry crossings between Thai islands? Partially. Short crossings (under 30 minutes) usually maintain patchy signal. Medium and long crossings have signal gaps mid-water. Treat ferry crossings as offline periods and prepare accordingly.
Is 5G available on Thai islands? Yes on major islands, Phuket has 5G in Patong and main tourist areas; Koh Samui has 5G in Chaweng. Smaller islands have 4G LTE at best. Your phone automatically connects to the best available signal.
Can I use hotspot on Thai islands for my dive buddy's phone? Yes, hotspot and tethering are supported on all our plans. In areas with weak signal, sharing one connection is better than two phones both struggling.
What should I download before taking the ferry to Koh Lipe or Koh Tao? At minimum: offline Google Maps for the island, your accommodation address, dive shop and tour operator WhatsApp contacts, and your ferry return schedule. Screenshot any Klook or accommodation booking confirmations to your camera roll.