Thailand has two diving regions on opposite calendars: the Andaman (Similans, Richelieu Rock, Phi Phi) from November to April, and the Gulf (Koh Tao, Samui) from March to September. Open Water certification costs 9,000–11,000 baht.
The short version
- Andaman for reef quality and big animals; the Gulf for learning cheaply.
- The Similan park closes mid-May to mid-October — no exceptions.
- Richelieu Rock needs a liveaboard; day boats cannot reach it.
- Koh Tao certifies more divers than anywhere else in the world, from about 9,000 baht.
The Andaman
The Similans and Koh Bon are the best sites in the country: granite boulders, visibility to 30 metres, manta rays at Koh Bon from February. The park closes May to October. Liveaboards from Khao Lak are the efficient way to do it.
Day trips from Phuket and Khao Lak reach Koh Haa and the King Cruiser, which are good rather than exceptional.
The Gulf
Koh Tao is the training island — thousands of certifications a year, cheap courses, and decent reef at Chumphon Pinnacle and Southwest Pinnacle. Visibility is best March to September.
Sail Rock, between Tao and Phangan, is the best single dive in the Gulf.
Choosing an operator
Ask for the certification level of your instructor, group size (four divers maximum per guide is a good rule) and whether insurance is included. Cheap courses with eight students per instructor are cheap for a reason.
What certification actually costs
Open Water certification on Koh Tao runs 9,000–11,000 baht, which is roughly $260–320, including gear, boat fees, materials and often accommodation for three or four nights. It is one of the cheapest places in the world to certify, which is why the island certifies more divers than anywhere else.
The Andaman is more expensive — 13,000–16,000 baht for Open Water out of Phuket or Khao Lak — because the boat costs are higher and the sites are further offshore. What you get for the difference is better visibility and, in season, the chance of a leopard shark on your qualifying dives.
Advanced Open Water is 8,000–10,000 baht on either coast, and it is worth doing in Thailand because the two specialty dives it includes — deep and navigation — are the ones that unlock most of the good Andaman sites. Nitrox is 300–500 baht a tank extra if you are diving several days.
