The long Than Sadet waterfall is probably the best known waterfall in Koh Phangan. It has the advantage of having water all the year long even at the worst of the dry season. It is a 3 km long waterfall composed with q succession of streams and pools where you can bathe, it is actually 3 waterfalls: Thong Nang, Sampon and Daeng waterfalls. The Than Sadet Waterfall is also very related to the Thai royalty with King Rama V true Koh Phangan fan who left its mark on a rock but also late King Rama IX. Regarding its length you have several access points, the easiest one being probably the one at the bottom of Than Sadet beach parking lot.