Namtok Than Sadet National Park

Namtok Than Sadet National Park protects a 2.5-kilometre river running through the jungle interior of Koh Phangan, spilling into a string of waterfalls and rock pools before reaching the sea near Thong Nai Pan. Foreign visitors pay around 100 THB adult entry (children generally free) — bring cash, as the park has no card facilities. The park was designated in November 2018 and covers roughly 43 square kilometres of forest.

The river’s name — Than Sadet, “royal river” — comes from King Chulalongkorn (Rama V), who visited in 1888 and, according to local tradition, carved his own initials into a boulder near the river estuary as several Thai kings before and after him also did on royal visits to the island. That carved rock is still there today, a low-key historical footnote most travellers here are chasing waterfalls rather than history for, but worth the short detour to see.

The forest itself is dense enough to shelter the Tiger Orchid (Grammatophyllum speciosum), one of the largest orchid species on earth, growing wild in the trees along the river valley — a genuine rarity rather than a garden specimen. Following the river inland leads past a sequence of waterfalls and pools deep enough to swim in, cool relief on an island where the beaches themselves run warm. For those wanting more than a swim, ATV tours and zip-line courses operate along sections of the trail.

The trail eventually reaches a small beach at the river mouth, with a handful of bars, restaurants, and simple guesthouses — a natural end point for a half-day out from the Thong Nai Pan side of the island rather than a full resort strip.

Insider Tip: Go on a weekday morning if timing allows — this stretch of Koh Phangan sees far fewer visitors than the island’s west-coast beaches, and the pools are at their best before groups arrive from organised ATV tours.

Safety Tip: Rip currents can form at the river mouth beach. Check the flag system before swimming, and if caught in one, swim parallel to the shore rather than fighting straight back against it.

The waterfall trail sits a short ride from Thong Nai Pan Yai Beach, the main beach on this side of the island, making it easy to combine a jungle-and-waterfall morning with a beach afternoon.