Thansadet beach is well known for its river and waterfall which meander down the mountain side through the dense jungle. For more than a century many Thai Kings have visited this magical place and carved their names upon the immense rocks that grace this river.

Located in the territory of Phangan island, that is Phangan island forest of national forest reservation, there are waterfall, forest and the animal is quite, then can develop the place of travel in future. The Royal Forest Department has surveyed; Phangan island forest of national forest reservation, Namtok Than Sadet forest, Khao Lat Kaeo forest, Khao Khai forest, Khao Ta Luang forest, Khao Hin Nok forest, Laem Pho-Laem Kata Khwa forest and Khao Fai Mai forest. Nowadays, in the processing has proclaim it to be a national park and using call of the name "Than Sadet - Ko Phangan National Park" , covers a total area of approximately 65.93 sq. km.

The landscape is high mountains, highest peak of the hills is Ra hill of 627 meters higher from the average sea level. The mountain forest is quite consists many island such as Phangan island, Tae Nok island, Tae Nai island, Ma island, Tung Ku islans, Tung Ka island, Wao islands and Hin Bai island, about 30 kilometers to the north form the Phangan island. Generlly the overlapping mountains and the plain stand by the valley and any of the bay area around the island.