Thailand's Best Islands: Andaman vs Gulf & How to Choose

Thailand has hundreds of islands scattered across two completely different seas, and choosing between them is the single biggest decision in planning a beach trip here. The Andaman coast in the west and the Gulf of Thailand in the east each have their own star islands, their own scenery, and — crucially — opposite weather patterns, so the "best" island depends entirely on what you want and when you're going. This guide compares the headline islands on both sides, explains the all-important monsoon timing, and walks through diving spots, the quiet-versus-party split, and the ferry and flight logistics that tie it all together.

Andaman side: Phi Phi, Lanta, Lipe and the Similans

The Andaman Sea, off Thailand's west coast, is the one most people picture when they imagine Thai islands: dramatic limestone karsts rising straight out of turquoise water, white-sand bays and world-class snorkelling. It's reached most easily through Phuket and Krabi, and the islands here range from full-on party hubs to barely-developed escapes.

Koh Phi Phi

The most famous of all, Koh Phi Phi is two main islands — Phi Phi Don, where you stay, and the uninhabited Phi Phi Leh, home to the celebrated Maya Bay. The scenery is genuinely spectacular, with sheer cliffs and impossibly blue lagoons. The trade-off is crowds and a lively, sometimes raucous nightlife scene in Tonsai village. It's a place you either love for the energy or use as a quick stop. If you're basing yourself nearby, our Krabi and Railay travel guide covers the mainland gateway and how to reach Phi Phi from Ao Nang.

Koh Lanta

Quieter and more spread out, Koh Lanta is a long island of laid-back beaches that gets calmer the further south you go. It suits couples, families and anyone after a slower pace, with easy scooter exploring, good seafood and a string of sunset-facing bays. It still has plenty of restaurants and bars but none of the Phi Phi intensity, which is exactly why many repeat visitors prefer it.

Koh Lipe

Right down near the Malaysian border, Koh Lipe is small, walkable and ringed by some of the clearest water in the country. Its compact "Walking Street" packs in restaurants and bars, while the surrounding Tarutao National Marine Park offers superb snorkelling. It's more remote and takes more effort to reach, but that's the point — it feels like a reward at the end of a longer journey.

The Similan Islands

The Similan Islands are a protected national park famous for diving and snorkelling rather than beach lounging, with granite boulders, pale sand and exceptional underwater visibility. They're typically visited on day trips or liveaboard dive boats out of Phuket and Khao Lak, and the park closes seasonally during the monsoon to protect the reefs, so they're a dry-season-only destination.

Gulf side: Koh Samui, Koh Phangan and Koh Tao

On the other side of the peninsula, the Gulf of Thailand islands cluster together in a convenient trio that's easy to hop between. The water is calmer and the islands more rounded and jungle-covered than the jagged Andaman karsts. They're reached via Koh Samui's airport or by ferry from Surat Thani on the mainland.

Koh Samui

Koh Samui is the largest and most developed of the three — effectively a resort island with its own airport, a full ring road, and everything from backpacker guesthouses to luxury spa resorts. Chaweng and Lamai are the main beaches, busy and well-equipped, while the quieter south and west coasts offer a gentler scene. It's the most convenient Gulf island to fly straight into. For a deeper look at the whole trio, see our dedicated Koh Samui, Koh Phangan and Koh Tao guide.

Koh Phangan

A short boat ride from Samui, Koh Phangan is world-famous for its Full Moon Party on Haad Rin beach, but that's only one corner of the island. Away from the party, the north and east are surprisingly tranquil, with secluded coves, yoga and wellness retreats, and a strong slow-travel community. It's a genuine two-sided island: choose your beach and you choose your experience entirely.

Koh Tao

Small, hilly Koh Tao is the diving heart of the Gulf and one of the cheapest places in the world to get scuba certified. It's packed with dive schools around Sairee Beach and Mae Haad, has a friendly backpacker-to-mid-range vibe, and offers easy snorkelling straight off several beaches. Even non-divers come for the relaxed atmosphere and the famous viewpoint over Nang Yuan, the tiny triple-islet just offshore.

Opposite monsoon seasons explained

This is the single most important thing to understand before booking, because the two coasts have roughly opposite weather. Get the timing wrong and you can land on an island during its rainiest, choppiest stretch while the other coast basks in sunshine.

Andaman coast (Phuket, Krabi, Phi Phi, Lanta, Lipe, Similans) — the dry, calm season runs broadly from November to April, with the wettest and roughest seas around the southwest monsoon from roughly May to October. Some smaller islands and the Similans effectively close in low season.
Gulf coast (Samui, Phangan, Tao) — the pattern is shifted. The Gulf islands enjoy some of their driest, sunniest weather around February to April and stay reasonably good through much of the year, but they get their heaviest rain late in the year, roughly October to December, which is peak Andaman season.

The practical upshot: if you're travelling in, say, November and want guaranteed beach weather, the Andaman side is the safer bet; if you're going in the deep wet months for the Andaman around mid-year, the Gulf islands often stay more pleasant. Because the seasons rarely line up perfectly, trying to combine both coasts in one trip means accepting that one side may be in its shoulder season. For a full month-by-month breakdown, read our guide to the best time to visit Thailand before locking in dates.

Diving and snorkelling hotspots

Both seas offer excellent underwater experiences, but they're known for slightly different things.

Koh Tao (Gulf) — the budget diving capital, ideal for beginners and certification courses. Calm, shallow sites and a huge concentration of dive schools make it the go-to for first-timers.
The Similan Islands (Andaman) — the premier destination for more experienced divers and serious snorkellers, prized for visibility, granite swim-throughs and the chance of larger marine life. Best reached on liveaboards or longer day trips and only open in the dry season.
Koh Lipe and Tarutao (Andaman) — superb, accessible snorkelling straight from the beach or on short longtail-boat hops, with healthy reefs in the surrounding marine park.
Koh Phi Phi and the Krabi area (Andaman) — plenty of day-trip snorkelling around the limestone islands, though popular sites can get busy with boats in high season.

Whichever you choose, remember you'll have no signal underwater or out at the dive sites, so screenshot your dive-school booking and meeting point in advance. Many operators take bookings and send confirmations through LINE or WhatsApp, which means having mobile data when you arrive makes coordinating pickups far smoother — a Thai eSIM keeps you reachable right up to the moment you step onto the boat.

Quiet islands vs party islands

One of the easiest ways to narrow your choice is to be honest about the kind of trip you want. Thailand's islands sit all along the spectrum from full-tilt nightlife to near-total seclusion.

For nightlife and a social scene

Koh Phangan — the Full Moon Party and a thriving year-round social scene around Haad Rin and Baan Tai.
Koh Phi Phi — beach bars, fire shows and a young, lively crowd packed into a small space.
Patong-adjacent island trips from Phuket — easy access to nightlife on the mainland resort strips, covered in our Phuket travel guide.

For peace, nature and slow travel

Koh Lanta — relaxed, family-friendly and spread out, with quiet southern beaches.
Koh Lipe — remote, scenic and far from the crowds despite its lively little main street.
The quiet side of Koh Phangan — wellness retreats and secluded coves away from Haad Rin.
Koh Tao — laid-back even with its dive crowd, especially outside Sairee's main strip.

Plenty of travellers split the difference by pairing one lively island with one quiet one — a night or two of buzz followed by a stretch of genuine downtime. Just remember that combining a Gulf and an Andaman island in the same trip adds significant travel time, which brings us to logistics.

Ferry and flight logistics between the islands

Getting around the islands is part of the adventure, but it pays to understand the broad geography so you don't plan an unrealistic route. The Andaman and Gulf clusters are on opposite sides of a long peninsula, and there's no quick boat between them.

Within the Andaman cluster

Phuket and Krabi act as the twin gateways. From there, ferries and speedboats connect to Phi Phi, Lanta and beyond, and these islands are reasonably easy to string together. Koh Lipe sits much further south and usually involves a longer ferry from the Pak Bara pier, making it more of a dedicated leg than a casual add-on.

Within the Gulf cluster

Samui, Phangan and Tao form a tidy triangle with frequent ferries running between all three, so hopping among them is straightforward and quick. You can fly directly into Koh Samui, or take a cheaper combined bus-and-ferry or flight-and-ferry connection via Surat Thani on the mainland.

Crossing between Andaman and Gulf

This is the big one: there is no direct island-to-island route between the two coasts. Crossing means returning to the mainland and travelling overland across the peninsula — typically a combination of ferry, bus or domestic flight via hubs like Phuket, Krabi, Surat Thani or Bangkok. Budget the best part of a day for it, and weigh whether a single coast suits your trip length better. Our two-week Thailand itinerary shows how to fit an island stretch around the cities without overreaching.

Across all of this, ferry schedules, speedboat bookings and Grab pickups at the pier all depend on a data connection, and signal can be unreliable at the exact moment you step off a boat. The smart habit is to download offline maps and screenshot every ticket and booking before you set out, then rely on mobile data to confirm onward connections as you go. You can browse Thailand eSIM plans sized by trip length so a multi-island hop never leaves you stranded at a ferry terminal without a signal.

Choosing between Thailand's islands really comes down to two questions: when are you going, and what are you after? Match the season to the right coast, pick a vibe from buzzing to blissfully quiet, and keep your route realistic given the distances involved. Sort out a Thai eSIM before you fly and you'll island-hop with maps, ferry apps and your group chat working from the first pier to the last sunset.

Frequently Asked Questions

Which is better, the Andaman or Gulf islands of Thailand?

Neither is universally better; it depends on timing and taste. The Andaman side (Phi Phi, Lanta, Lipe, the Similans) has dramatic limestone scenery and is best from roughly November to April. The Gulf side (Samui, Phangan, Tao) has calmer water, an easy island-hopping triangle, and tends to be drier around February to April while staying decent when the Andaman is at its wettest. Choose the coast whose dry season matches your travel dates.

Can I visit both the Andaman and Gulf islands in one trip?

Yes, but plan for the travel time. There is no direct boat between the two coasts, so crossing means returning to the mainland and going overland or flying via hubs like Phuket, Krabi, Surat Thani or Bangkok, which can eat the best part of a day. Because the monsoon seasons are roughly opposite, one coast may be in its shoulder season whenever you go. For shorter trips, sticking to one cluster is usually more rewarding.

Is Koh Samui or Phuket better for a beach holiday?

Phuket is larger, busier and the main Andaman gateway, with the widest range of beaches, nightlife and day trips to islands like Phi Phi and the Similans. Koh Samui is a more self-contained Gulf resort island with its own airport, calmer water and easy ferries to Koh Phangan and Koh Tao. Pick Phuket for variety and Andaman scenery in the November-to-April window, or Samui for a relaxed Gulf base, especially around February to April.

Which Thai island is best for diving and snorkelling?

For learning to dive on a budget, Koh Tao in the Gulf is the go-to, with calm sites and many affordable certification schools. For more experienced divers and top-tier snorkelling, the Similan Islands on the Andaman side are famous for visibility and marine life, reached by liveaboard or day trip from Phuket and Khao Lak during the dry season. Koh Lipe also offers excellent reef snorkelling straight from the beach.

Which Thai islands are quiet and which are party islands?

For nightlife, Koh Phangan (the Full Moon Party) and Koh Phi Phi are the liveliest. For peace and slow travel, Koh Lanta, Koh Lipe, the quiet north of Koh Phangan and much of Koh Tao away from the main strip are far more relaxed. Many travellers pair one lively island with one quiet one, keeping in mind that combining a Gulf and an Andaman island adds significant overland travel time.