Khao Yai National Park is situated in the western part of the Sankamphaeng Mountain Range, at the southwestern boundary of the Khorat Plateau. The highest mountain in the area of the park is 1,351 m high Khao Rom.
This park lies largely in Nakhon Ratchasima Province (Khorat), but also includes parts of Saraburi, Prachinburi and Nakhon Nayok provinces.
The park is the third largest in Thailand. It covers an area of 2,168 square kilometers, including evergreen forests and grasslands. Its altitude mostly ranges from 400 to 1000 m above sea level. There are 3,000 species of plants, 320 species of birds like red junglefowl and Coral-billed Ground-cuckoo and 66 species of mammals, including Asiatic black bear, Asian elephant, gaur, gibbon, Indian sambar deer, pig-tailed macaque, Indian muntjac, dhole, and wild pig. Although evidence of tiger presence has not been recorded recently, monitoring by FREELAND Foundation in collaboration with Department of National Park rangers has discovered tigers (the Indochinese tiger subspecies) in other parts of Eastern Thailand where they were previously thought to have been completely extirpated. Its waterfalls include the 80 metre Heo Narok, and Heo Suwat made famous from the film The Beach. Namtok Sarika is popular with the Thais.
Recent wildlife studies show that animal ranges, particularly the few resident tigers, are impacted by human activity near the center of the park. This study has not impacted the government's call for private lodging concessions within the park itself.