Thailand's coastline stretches over 3,200 kilometres across two seas — the Andaman on the west and the Gulf of Thailand on the east. The result is one of the world's most varied beach landscapes, from limestone karst cliffs plunging into emerald water to endless white-sand stretches lined with coconut palms.
Andaman coast — the postcard classics
Railay Beach in Krabi is unreachable by road and requires a short longtail boat ride from Ao Nang. That isolation preserves its dramatic beauty: sheer limestone walls, powdery sand and warm shallow water. It is also one of Asia's finest rock-climbing destinations, with hundreds of bolted routes on Tonsai and Phra Nang beaches.
Maya Bay on Koh Phi Phi Leh — made famous by the 2000 film The Beach — was closed for four years to allow coral regeneration and reopened in 2022 with strict visitor caps (no swimming, timed entry). Book with certified operators from Phi Phi Don or Krabi.
The Similan Islands (Mu Ko Similan National Park) north-west of Phuket open only from mid-October to mid-May and offer some of the clearest water in Southeast Asia. Overnight tent camping is possible on Similan Island 4 with advance booking.
Gulf coast — mellower, greener
Koh Samui remains the most developed island on this side, with a full airport and international flights. Chaweng is busy and lively, Bophut is quieter and family-friendly, and the northern coast around Maenam is where locals go.
Koh Tao is legendary for diving — you can complete a PADI Open Water certification in three days for around 12,000 THB. Shark Bay and Aow Leuk are excellent for snorkelling straight from the beach.
Koh Kood (also spelled Koh Kut), close to the Cambodian border, remains one of the least developed larger islands. Klong Chao and Bang Bao beaches are unspoiled, with warm water year-round and just enough accommodation to be comfortable without feeling touristy.
Off the beaten path
Koh Lipe, near the Malaysian border in the Adang Archipelago, is a small island of only 3 km² with three main beaches: Sunrise, Sunset and Pattaya. The water clarity here rivals the Maldives, and prices remain reasonable outside December-January peak.
Koh Kradan, also in Trang province, was voted the world's best beach by World Beach Guide in 2023. Almost no motor traffic, one long white beach on the west side, and just eight small resorts.
When to go
Andaman coast (Phuket, Krabi, Phi Phi, Similan): best from November to April, dry and calm. May-October brings the southwest monsoon with rough seas.
Gulf coast (Samui, Phangan, Tao, Kood): best from January to April and June-September. October-December can bring heavy rain, especially November.
Practical tips: bring reef-safe sunscreen (mandatory in many national parks since 2022), avoid touching or standing on coral, and always use the yellow buoy anchor system when snorkelling. Longtail boat prices are usually posted at each pier — pay only the official rate.