It is a craggy wooded island and a great part of its coast is formed by rocky cliffs even if some sandy beaches are present in the northern and eastern sides.

This island is at the southeastern end of the Bay of Bangkok, on the east side of the Gulf of Siam.

Administratively Ko Phai belongs to the Amphoe Bang Lamung, Chonburi Province.

All these islands are a protected natural area under the supervision of the Royal Thai Navy.

A World War II-vintage ship of the Royal Thai Navy, HTMS Khram (ex-USS LSM-469), was sunk 300 m to the east of Ko Phai in January 2003 in order to create an artificial submerged reef.