Map of Thailand showing the locations used during the making of the movie: (1) Phi Phi Le island, (2) Phuket, (3) Krabi and (4) Khao Yai National Park.
This is the famous map drawn by Daffy which shows the way to the "secret lagoon" and the beach. The island is actually fictitious, but the places mentioned in the book and movie are real. For example, Surat Thani and the islands Koh Samui and Koh Pha Ngan.