A clan of Chao Ley, or "sea gypsies" lives on Ko Lanta Yai. The clan still practices many of their ancient customs and ceremonies, such as the setting of ceremonial boats adrift to bring good luck and prosperity on the full moon nights of the sixth and eleventh months.
Ko Lanta was once known by its Malay name, "Pulao Satak", which means "Long Beach Island". Later, many Thais, both Buddhist and Muslim, moved to the island making the island known as the island of "a million eyes" ("lan ta" in Thai). The name may also be derived from the Javanese "lan-tas", or fish grill (built of wood with a square grill on top where the fish are placed in a circle).
The area of Mu Ko Lanta National Park is 134 km2 (83,750 rai. It includes Mu Ko Rok, Ko Mai Ngam, Ko Talabeng, Ko Lanta Yai, Ko Ngai, Mu Ko Rokk, Ko Rok Nai, Mu Ko Maa, Ko Hin Dang and the nearby islands of Ko Klang, Ko Lanta Noi, and Ko Lanta Yai sub-district, Amphoe Ko Lanta, Krabi Province.
The terrain is mountainous, especially near the southern tip. Plains are found only in beach areas in the southern portion of the park. Most areas have more than a 35 degree slope, except only the middle part of island where the slope is more than 50 degrees. Elevations range from sea level to 488 meters at the tallest peak.
Highest rainfall is in September, 391.4 mm, and lowest in January at 6.5 mm. September has the most rainy days with 21.6 days and February the fewest, about 1.6 days. During the rainy season, 16 May-31 October, some smaller islands are closed to visitors.
The animals that live on the islands are divided into six categories.
1. Mammals: deer, tigers and barking deer.
2. Birds: brahminy kite, bridled tern, and emerald dove.
3. Reptiles: water monitor lizards, reticulated pythons, and cobras.
4. Amphibians: giant mountain frogs, ornate froglets, and Polypedates leucomystaxs.
5. Freshwater fish and marine fish: blue danio fish, coral reef fish, and lizard fish.
6. Coral reef animals: staghorn coral, Fungia fungites, and anemone coral.
The plants in Mu Ko Lanta National Park can be categorized into three groups.
1. Rainforest: The total area of rainforest at Mu Ko Lanta Yai is about 19.42 km2. The average height of trees is 15–25 meters. The important plants are Hopea Ferrea Laness, Dipterocarpus Tubinatus C.F. Gaertn, and Lagerstroemia Floribunda Jack.
2. Mangrove forest: On Ko Ngu, Ko Mai Ngam, and Ko Mai Ngam Tai. The average height of trees is five meters. There are many plants in the mangrove forest, such as Avicennia alba, Rhizophora apiculata, and Rhizophora mucronata.
3. Beach forest: Found on Ko Ngai between the beach and rainforest. Significant plants are Bengal almond, Derris indica, and beach morning glory.