Diving in Thailand — Complete Guide to Andaman & Gulf Diving

Thailand's diving divides cleanly into two regions, each with its own season, character, and logistics.

The Andaman Sea (west coast) stretches from the Myanmar border south to the Malaysian border, with the primary diving bases at Phuket and Khao Lak. The Similan Islands — a chain of nine granite islands 60 nautical miles offshore — are the centrepiece, accessible only by liveaboard or long day trips from Khao Lak. The Similans offer granite boulder formations, swim-throughs, and cleaning stations where manta rays are regularly encountered from February to April. North of the Similans, Richelieu Rock is a horseshoe-shaped pinnacle famous for whale shark sightings and extraordinary macro life. Further south, Hin Daeng and Hin Muang are deep-water pinnacles with dramatic walls, mantas, and occasional whale sharks. The King Cruiser wreck near Phuket provides accessible wreck diving at 12–32 meters.

The Gulf of Thailand (east coast) is dominated by Koh Tao, a small island in Surat Thani province that has become the world's most popular destination for learning to dive. The island offers over 25 dive sites within a 30-minute boat ride, with Sail Rock — a massive granite pinnacle 20km offshore — as the premier advanced site. Chumphon Pinnacle provides regular encounters with bull sharks and large groupers. The Gulf is calmer, warmer, and shallower than the Andaman, making it ideal for training and early diving experience.

Coast comparison at a glance — Andaman Sea: season October–May, 15–30m visibility, manta and whale shark encounters, liveaboard access to remote sites, higher prices. Gulf of Thailand: year-round diving, 5–20m visibility, lowest certification prices globally, easy island-hop logistics, best for training.

Liveaboard diving operates primarily from Khao Lak and Phuket during the Andaman season (October–May). The standard itinerary covers the Similan Islands, Koh Bon, Koh Tachai, Richelieu Rock, and occasionally the Surin Islands. Premium routes add Hin Daeng/Hin Muang and the Burma Banks. Liveaboard prices range from $240 for a 2-night budget trip to $2,500+ for a 7-night premium expedition. Most trips include food, diving, park fees, and standard equipment.

Dive training in Thailand is exceptionally well-organised. PADI, SSI, and RAID courses are available at every level, from Discover Scuba to Instructor Development. Koh Tao leads in volume (prices from 8,500 THB / $250 for Open Water), but Phuket and Khao Lak offer equally professional training with quieter conditions and resort-style comfort at slightly higher prices (12,000–15,000 THB / $340–430).

Travel logistics: Thailand grants visa-free entry (30 days) to citizens of 57 countries including the US, UK, EU, Australia, and most of Southeast Asia. Extensions of 30 days are available at immigration offices for 1,900 THB. Phuket (HKT) has direct international flights from most Asian hubs and seasonal European charters. Koh Tao is reached via Surat Thani airport + ferry (total ~4 hours) or overnight train from Bangkok + morning ferry. Internal flights between coasts (Bangkok–Phuket, Bangkok–Surat Thani) cost $30–80 on AirAsia or Nok Air.

Budget planning: A week of diving in Thailand costs $500–2,500 depending on location and style. Budget example (Koh Tao, 7 days): Open Water course $300 + 6 fun dives $180 + accommodation $150 + food $100 = ~$730. Mid-range example (Phuket + liveaboard, 10 days): 4-night liveaboard $800 + 2 Phuket day trips $200 + hotel $500 + food $200 = ~$1,700. Premium example (full Andaman, 14 days): 5-night premium liveaboard $1,500 + 4 Phuket day trips $500 + resort $1,200 + food $400 = ~$3,600.

Typical itineraries: 1 week (beginner) — Fly to Koh Tao, Open Water course (3–4 days), fun dives at Japanese Gardens and Sail Rock, depart. 10 days (intermediate) — Fly to Phuket, 2 days of day trips (Shark Point, King Cruiser, Racha), transfer to Khao Lak, 4-night liveaboard (Similans + Richelieu), return Phuket for departure. 2 weeks (advanced) — Phuket day trips + nitrox course (3 days), Khao Lak liveaboard (5 nights, extended route with Hin Daeng), fly to Koh Tao for Gulf diving and Sail Rock (4 days), depart via Surat Thanifessional instruction with smaller class sizes.

Thailand works for literally every level. Complete beginners flock to Koh Tao for affordable, high-quality certification courses. Intermediate divers enjoy the Similan liveaboard circuit. Advanced and technical divers target Richelieu Rock, Hin Daeng, and the deep pinnacles. Freedivers have a growing scene on Koh Tao and Koh Lanta. Underwater photographers rate Richelieu Rock among the top macro sites in the world.

Thailand has two distinct diving seasons determined by the monsoons. Andaman Sea (west coast): October–May, with peak conditions January–April. The Similan Islands National Park is officially open November 1 – May 15. Gulf of Thailand (east coast): year-round diving, with best visibility March–September. October–December brings occasional storms but also whale shark season at Sail Rock. Crossover months (March–April) allow diving both coasts.