Close to the mainland in the southeast corner of Krabi province, Ko Lanta is a group of 52 islands, 15 of which belong to the Ko Lanta National Marine Park. Most of the wildlife can be found on the smaller, remoter islands. The ramshackle wooden port of Ban Sala Dan is the gateway to Ko Lanta Yai , a predominantly Muslim fishing island. Some 25 km (15 miles) long, this is the main island in the archipelago. It is covered with undulating forested hills sweeping down to numerous west-facing sandy bays. The natural beauty has attracted many new resorts, and Ko Lanta Yai is now popular with tourists. However, monkey and lizard footprints are still more common on its beaches than human prints.

The Laem Kaw Kwang headland in the northwest of the island has views across to Ko Phi Phi. At the southern tip, a 3-km (2-mile) coastal trail leads to a solar-powered lighthouse on a steep promontory beside the park headquarters.

Sea gypsies inhabit the nearby village, Ban Sangka-u. They are renowned for their colorful rituals, such as the loi rua  ceremony. As part of the festivities, a 2-m (6-ft) replica boat is sent out to sea to banish the ill fate built up throughout the past year.