koh Samui is in the Gulf of Thailand, about 35 km northeast of Surat Thani town (9°N, 100°E). It is the most significant island in the Chumphon Archipelago. The island measures some 25 km at its widest point. It is surrounded by about sixty other islands, which together compose the Ang Thong Marine National Park (Mu Ko Ang Thong National Park) and include many other popular tourist destinations, including, Ko Pha Ngan, Ko Tao, and Ko Nang Yuan.