Ko Lanta Yai Thailand Ko Lanta Yai A Ko Lanta beach Ko Lanta Yai is located in the Andaman Sea off the west coast of Thailand, between the Phi Phi Islands and the mainland. They are politically part of Krabi Province, most of which is on the mainland. Measuring 30km long and 6km wide, the island forms part of the Ko Lanta archipelago, which covers an area of 180 km. The