The national park covers the southern third of Ko Lanta Yai and several uninhabited islands in the surrounding sea. The main entrance is at the southern tip of the island, where a lighthouse stands on a rocky headland above the sea. Trails lead through the coastal forest, and the beaches within the park — particularly Haad Nui, accessible only by foot or kayak — are among the least visited and most beautiful on the island.
The park also protects the coral reefs around Ko Rok Nok and Ko Rok Nai, two islands about 25 km offshore that offer some of the best snorkelling in the Andaman Sea. Day trips to Ko Rok leave from piers on the main island and are the highlight for most visitors. The clearest water and best visibility are from November to April.