Koh Mak is located 40 KM away from the coastline of Trat province. Koh Mak, with an area of 16 square kilometers and a 27 kms coastline, is the third largest island of the Marine Park. It has a flat terrain with plenty of coconut and rubber plantations.

The main attractions are the long beaches and clear seawaters. There are only a few hundred people living here. There are about 10 resorts mostly situated at the northwest or southwest of the island. Infrastructure on the island is limited but there is a road system that conveniently link up the island. Ao Suan Yai, to the northwest has the longest and most beautiful beach where you can view Koh Raet, Koh Phee, Koh Kham as well as the captivating sunset. The beach is lined with coconut trees. There are some fine restaurants here too. During low tide a sand dune appears between Koh Mak and Koh Kham allowing you to walk across. Ao Khao on the southwest is another spectacular site of fine beach with clear waters and great views of Koh Kood, Koh Rayang Nai, Koh Rayang Nok and the beautiful sunset. There are some reefs teening with plentiful of fishes and is a favorite site for the anglers.