Best Thai Islands for Diving: Sites, Courses & When to Go

Thailand is one of the world's most accessible and affordable scuba diving destinations — with PADI Open Water courses costing ฿9,000–14,000 (vs ฿30,000+ in European locations), exceptional marine biodiversity, and diving conditions suitable for all levels. The top diving destinations: Koh Tao (Gulf of Thailand) — the global capital of affordable dive certification; over 50 dive schools, shallow clear bays perfect for beginners, and enough advanced sites (Chumphon Pinnacle, Southwest Pinnacle) for experienced divers; whale sharks seen regularly March–April. Similan Islands (Andaman, day trips from Khao Lak) — one of Asia's top 5 diving destinations; extraordinary marine biodiversity, cleaning stations with manta rays and whale sharks (January–May), dramatic underwater landscapes. Richelieu Rock (near Koh Surin) — regularly ranked among the world's top 10 dive sites; manta rays and whale sharks from January–April. Koh Lipe — excellent shore and boat diving with pristine coral and outstanding visibility in the Andaman's far south. For liveaboard diving: operators from Khao Lak and Phuket run 3–7 day Similan/Surin liveaboards from ฿15,000–40,000 per person all-inclusive. The Mergui Archipelago (accessible from Ranong) is for experienced divers seeking more remote, less-visited sites. Best overall season: November–April for Andaman; April–October for Gulf. Water temperatures are warm year-round (28–30°C).