There is no single best island. Koh Lanta is best for quiet, Koh Tao for diving and value, Koh Samui for families and resorts, Koh Phangan for yoga and the Full Moon Party, and Koh Lipe for the clearest water. The Andaman and Gulf have opposite seasons.
The short version
- Quiet: Koh Lanta or Koh Phangan's north coast.
- Diving: Koh Tao (cheap certification) or the Similans (best reef).
- Families: Koh Samui, particularly Choeng Mon and Maenam.
- Clearest water: Koh Lipe and the Tarutao group, December to April.
For quiet
Koh Lanta and Koh Yao Noi. Long beaches, few people, no nightlife to speak of. Koh Lanta is easier to reach and has more restaurants.
Koh Kood, near the Cambodian border, is the quietest of all but the transfer is long and the hotels are limited.
For diving and snorkelling
Koh Tao for courses and cheap accommodation; the Similans for the best sites in the country, reached by liveaboard from November to April.
Koh Haa and Koh Bida, off Krabi and Lanta, are the best day-trip diving on the Andaman coast.
For families
Koh Samui: calm water on the north coast, short transfers, good hospitals. Phuket's Kata beach is the other reliable choice.
Avoid Koh Phangan's Full Moon area with children, and avoid long-tail transfers with very young kids.
For parties
Koh Phangan for the Full Moon Party, Koh Phi Phi for the beach bars, Pattaya if you want it all within walking distance. None of these are quiet, and none pretend to be.
Getting between the islands
The most common planning mistake is assuming islands that look close on a map are close in time. Krabi to Koh Lanta is a two-hour car ferry; Phuket to Koh Phi Phi is a 45-minute speedboat but two hours by ferry; Surat Thani to Koh Samui is 1.5 hours by catamaran and 45 minutes by plane. Every transfer eats at least half a day.
The practical rule is one island per week, plus a mainland base. Two islands in seven days is workable if they are in the same group; two islands in different seas — say Samui and Lanta — is a day of travel and should be avoided unless the trip is three weeks long.
The Gulf islands (Samui, Phangan, Tao) connect easily to each other by Lomprayah catamaran, which is the fastest and most reliable operator. The Andaman islands connect via Krabi or Phuket, and the smaller ones — Koh Lipe especially — are only reachable in the high season.
