Phuket is easy. Central Samui is easy too. If your phone works perfectly in Patong, Chaweng or beside a ferry terminal, that tells me almost nothing about how useful the same connection will feel later on Koh Kood, southern Koh Lanta or a longtail trip away from Koh Lipe.

I therefore choose for the weakest part of the itinerary. If I am doing Phuket, Phi Phi and Lanta, I choose for Lanta rather than Phuket. If I am doing Samui, Phangan and Tao, I choose for Tao. If I am combining Chang, Mak and Kood, Koh Kood sets the standard.

Thailand’s network picture has changed because True and dtac now operate on integrated infrastructure. I explain that properly in my AIS vs True/dtac Thailand network comparison, so I will not repeat the whole national analysis here.

For island travel, my conclusion is simpler. AIS remains my preferred starting point for a route that includes several islands, while True/dtac can be excellent in developed beach zones and heavily visited destinations. The distinction becomes important when you leave those easy areas.

AIS: My Default for Island Hopping

AIS has been the most consistent choice across the widest range of island environments we have tested. That does not mean it is always the fastest at the hotel or that it has signal in every bay, but it gives me the best margin when the day includes scooter rides, viewpoints, quieter beaches and ferry transfers.

I also like the way AIS tends to recover after a weaker stretch. When I am navigating between beaches, that reconnection behavior is often more useful than a spectacular speed test beside a resort.

True/dtac: Very Good in the Developed Island Zones

I would not avoid True/dtac on a Phuket or Samui trip. The main tourism zones are well served, and the integrated network has continued to improve around heavily traveled areas, including Koh Phangan.

My hesitation starts when the route becomes less conventional. For several-island itineraries, I would rather choose the network that gives me the broadest margin across the whole route than optimize for one resort strip.

Between my own Thailand trips and testing by other people on our team, we have used mobile data for scooter navigation, ferry details, restaurant searches, hotel messages, ride pickups, maps and ordinary browsing across these islands. The main towns were rarely where the differences became interesting.

What exposed the networks was movement. Hills, headlands, quieter beaches, ferry areas and longtail routes were much more revealing than standing in the middle of a developed resort zone.

Phuket: The Easy Island

Phuket has enough infrastructure that I would not make network choice the center of a Phuket-only eSIM decision. Patong, Kata, Karon, Rawai and Bang Tao were straightforward for normal travel use, and all major Thai network options are realistic in the developed zones.

The reason I still lean AIS is what usually happens next. Many Phuket trips continue to Phi Phi, Lanta or other Andaman islands, and I would rather choose for the full route than save a tiny amount on the easiest island.

Koh Samui: Strong Coverage Around the Ring Road

Samui is another island where the main traveler zones are relatively easy. Chaweng, Lamai, Bophut and Maenam all sit inside well-developed coastal areas, and I have no issue recommending either AIS or a good True/dtac-based option for someone staying mostly there.

AIS remains my preference when I know I will keep moving. Once I am exploring quieter parts of the island or combining Samui with Phangan and Tao, I prefer choosing for the whole Gulf route.

Koh Phangan: Easy Around the Main Areas, Less Predictable in the Hills

Around Thong Sala, Baan Tai, Haad Rin and the better-developed west coast zones, mobile data is generally straightforward. True has also continued investing in coverage around Phangan, so this is not a case where AIS is the only sensible network.

I still prefer AIS for people who actually explore the island. When the road climbs, a beach sits behind a headland or the route leaves the busy coastal zones, I care much more about how quickly the connection returns than about the maximum speed I saw in town.

Koh Tao: Small Island, Surprisingly Uneven Signal

Koh Tao is compact, but its terrain makes it more variable than its size suggests. Sairee and Mae Haad are the easy parts, while viewpoints, smaller bays and some inland routes can make the signal considerably less predictable.

I would start with AIS and still download what I need before a scooter day or dive trip. If a dive operator sends meeting details or a ferry ticket electronically, I want that information saved locally rather than trapped behind a connection I may not have later.

Phi Phi: Fine in Town, Much Less Useful on the Water

Tonsai and Loh Dalum are not difficult places to stay connected. The distinction appears once you leave the central area and get onto a longtail boat, which is exactly what most visitors eventually do.

Around Maya Bay, Pileh Lagoon, Bamboo Island and open-water stretches, I treat mobile data as a bonus. I save tickets, meeting points and anything I need for the return journey before I leave Phi Phi itself.

Koh Lanta: One of the Islands Where I Care About the Network

Lanta is long, spread out and much less uniform than Phuket. The west coast beach areas were generally comfortable for normal mobile use, but the farther south or inland I went, the more useful it became to have the network I trusted most.

This is one of the islands where I would not overcomplicate the decision. If Lanta is a meaningful part of the trip, I would start with an AIS-capable eSIM and then compare providers that give me that access.

Koh Chang: West Coast First, More Uncertainty Elsewhere

White Sand Beach, Klong Prao and Lonely Beach were straightforward enough for everyday travel use. AIS was the network I trusted most while moving between those areas rather than remaining beside one hotel or restaurant.

The east coast is quieter and much less developed, so I would expect more gaps regardless of provider. If your trip includes a lot of exploring rather than a fixed beach stay, that is another reason I choose coverage before price.

Koh Kood: This Is Where I Stop Pretending Coverage Is Continuous

Koh Kood is quieter, greener and more spread out than Thailand’s big resort islands, and mobile service reflects that. AIS was the best option in our experience, but even AIS is not something I would treat as a permanent connection across every road and beach.

My expectation here is practical rather than unrealistic. I want enough connectivity for maps, messages and reconnection after weak stretches, but I still keep offline navigation ready before getting on a scooter.

Koh Mak: Easier Than Kood, but Usually Part of the Same Route

Koh Mak itself is less demanding than Koh Kood, and normal data use around the main beach areas was not a major problem. I still choose AIS because very few people are making a network decision for Koh Mak in isolation.

It is commonly combined with Chang or Kood, so I choose the network that makes sense across all three. That is the same route-first principle I use throughout this guide.

Koh Lipe: The Beach Can Be Fine While the Boat Has Nothing

Pattaya Beach and Sunrise Beach are the easy parts of Koh Lipe. Once I am on a longtail toward Koh Adang, Koh Rawi or smaller islands, I stop expecting the connection to follow me reliably.

AIS is still my first choice, but I save everything important before leaving shore. An eSIM is useful here; it is not a substitute for basic offline preparation.

Mobile data often stays available close to a pier or while the boat is still hugging a populated coastline, but I never plan around having service for an entire crossing. Once there is enough water between the phone and the nearest useful tower, the connection can weaken quickly or disappear.

This matters most for exactly the information travelers leave online: QR tickets, hotel addresses, pier names, transfer confirmations and messages from boat operators. Before boarding, I save the things I cannot afford to discover are inaccessible later.

The same logic applies to scooter navigation. I use live Maps constantly, but I download offline maps before exploring quieter parts of Koh Tao, Lanta, Chang or Kood because the precise moment I lose signal is usually the precise moment I want to know whether I missed a turn.

Connectivity is only one part of island preparation. For ferries, humid weather, beach days and scooter travel, I also recommend this Thailand packing guide, which is a useful companion resource before you leave.

For normal travel, I care about maps, messaging, bookings, tickets and being able to reconnect after a weak stretch. If I am working from Thailand, I care much more about sustained uploads, hotspot rules, video calls, peak-hour stability and having a backup when accommodation Wi-Fi disappoints me.

I have worked online from Thailand myself, so I keep that analysis separate rather than pretending the same ranking answers both questions. If you are spending weeks working from Samui, Phangan, Phuket or elsewhere, use my Thailand eSIM guide for digital nomads.

Once I know the route and the Thai network access I want, I compare the actual eSIM products. I usually start with Nomad, then check Airalo and Yesim to see whether one of their current plans fits the trip better.

I do not permanently assign one international provider to one Thai carrier because those partnerships and individual plan details can change. The host network shown on the exact plan is more important than what the same company happened to use on a previous trip.

The first option I usually check

Nomad Thailand eSIM

Nomad is usually my starting point when I want a Thailand eSIM before arrival, particularly for a trip with several stops. I can install it before flying and avoid dealing with a physical SIM immediately after landing.

For an island itinerary, I still inspect the current plan details before paying. If a suitable plan gives me AIS access, that fits the coverage-first approach I use for Lanta, Kood, Lipe and other less forgiving stops.

Best fit: multi-island trips where I want the eSIM ready before arrival

What I check: the current Thai network or networks listed on the exact plan

My preference: AIS access for routes containing quieter or more remote islands

Do not forget: download ferry information and offline maps regardless of provider

Check Nomad Thailand eSIM Plans

For a route involving several Thai islands, I would start by finding a good eSIM with AIS access and then compare the available plans from providers such as Nomad, Airalo and Yesim. I would make the decision based on the hardest island or route segment, not on whichever provider looks fastest in Bangkok or cheapest for one gigabyte.

If I were staying only in Phuket, Samui or another highly developed area, I would be much more flexible and happily use True/dtac access when the plan was better. Once my itinerary included Tao, Lanta, Kood, Lipe or several boat transfers, I would become more conservative and prioritize coverage.

The bigger lesson from our testing is that island connectivity is rarely about having no signal for an entire trip. It is about the annoying gaps between good coverage zones, and those are exactly the moments when I want my phone working for Maps, ferry details or a hotel message.