Mu Ko Phetra National Park

Mu Ko Phetra National Park protects around 30 islands scattered off the Satun coast near the Malaysian border, established in 1984 and covering roughly 494 sq km of land and sea. Entry costs 100 THB for foreign adults (50 THB for children), 20/10 THB for Thai nationals, paid at Pak Bara Pier or on arrival at the island. Two of the park’s best-known islands close for the southwest monsoon each year, so check the calendar before you plan a trip around them.

The main islands are Koh Phetra itself, distinctive for its eroded limestone cliffs; Koh Khao Yai, the largest in the group, with karst formations rising straight from the water; Koh Lidi, reached only by charter boat since no ferry runs there; Koh Bulon Le, the most developed of the group with a daily ferry and a small resort scene; and the twin islands of Koh Lao Liang, once known for climbing on their bolted limestone cliffs. That’s changed: the park has since banned climbing on Koh Lao Liang and closed the tented camp that supported it, so the islands today are a snorkelling stop rather than a climbing destination. Elsewhere in the park, shallow reef around the smaller islands holds parrotfish and other reef fish in clear water, and dolphins are occasionally spotted from the boat between islands.

Koh Bulon and Koh Lao Liang close to visitors during the southwest monsoon, roughly 1 June to 30 September: no boats run, and camping isn’t permitted on either island during that window. The rest of the park stays open year-round, but the calmest crossings and best underwater visibility are during the dry season, November to April.

Insider Tip: Koh Lidi has no scheduled ferry, which keeps it quieter than Koh Bulon. Arrange a charter boat at Pak Bara Pier a day ahead rather than turning up expecting to find one on the spot.

Watch out: Older dive guides and blogs still list Koh Lao Liang as a climbing destination. It isn’t any more: the ban is current park policy and rangers are stationed on the islands to enforce it.

Koh Bulon has the park’s only scheduled ferry and its own small resort scene, while Koh Khao Yai and Prasat Hin Pan Yot covers the largest island’s limestone formations in more detail. For what’s changed on the twin islands since the climbing camp closed, see Koh Lao Liang, worth reading before you book a trip built around climbing there.