Ko Samet is one of the Eastern Seaboard Islands of Thailand. It is located in the Gulf of Thailand off the coastline of the Thai province of Rayong, approximately 220 kilometres (140 mi) southeast of Bangkok. Ko Samet is part of the Subdistrict of the Amphoe Mueang Rayong the capital district, or Amphoe Mueang), of Rayong province. Ko Samet is the largest and westernmost of a cluster of islands not far from the coast.
Popular with foreign tourists and as a weekend getaway for residents of nearby Bangkok, most of the island (excluding the Na Dan area) belongs to the Khao Laem Ya - Mu Ko Samet National Park. In 1981, the Royal Forest Department declared the archipelago of Samet, along with nine other small islands, the headland of Khao Laem Ya, and the 11 kilometres (6.8 mi) Mae Ramphueng Beach to be a National Park, and is thus Ko Samet is under the protection of the National Parks Division of the Thai Government.
Ko Samet is 6.5 kilometres (4.0 mi) south of mainland Rayong province and is surrounded by the Gulf of Thail