Ko Wai (Thai: เกาะหวาย) is a small island in Ko Chang Archipelago, Trat Province, eastern Thailand.

Ko Wai Island has an irregular shape and is 3 km long and 1 km wide at the widest point.

The east part of the island is encircled by coral reef and has sand beaches while the west part is more rugged and hilly, and serves as a nesting ground for birds.

There are four bungalow operations on the island and daily boat connections to Ko Chang, Ko Mak, and the mainland, during the season.

[1] The island is a protected area and it is part of Mu Ko Chang National Park.