Koh Samui is an island belonging to Surat Thani Province, off the east coast of the Kra Isthmus in Thailand, close to the town of Surat Thani on the mainland.
The island is roughly circular in shape, and is about 15 km across. The central part of the island is an almost uninhabitable mountain jungle, Khao Pom, peaking at 635 m. The various lowland areas are connected together by a single 51 km road, running mostly along the coast to encircle the bulk of the island.
Ko Samui Airport is a private airport. Several ferries connect the island with the mainland, including the car ferry from Don Sak to a pier in the west of the island, south of the main town Nathon. Public buses to all parts of the mainland operate from a small bus station located in the south of Nathon
Ko Samui, being in Surat Thani Province, has essentially two seasons; warm and tropical most of the year, with a short rainy season. Samui's weather is relatively dry for the vast majority of the year. For the rest of the year, since the weather is tropical, when it does rain, it usually doesn’t last long; rain showers of 20–60 minutes are typical.