Ko Samui is located in the Gulf of Thailand, about 35 km northeast of Surat Thani town (9°N, 100°E). The island measures some 21 kilometres at its narrowest point, and 25 km at its longest. It is surrounded by about sixty other islands, which compose the Ang Thong Marine National Park (Mu Ko Ang Thong National Park) and include other tourist destinations (Ko Phangan, Ko Tao and Ko Nang Yuan).