The park, which covers an area of 2,168 square kilometers in the Phanom Dong Rak mountain range, stretches over 4 provinces including Nakhon Ratchasima, Nakhon Nayok, Saraburi, and Prachin Buri. Khao Yai became Thailands first national park on 18th September 1962 and is also originally recognized as the National Park Heritage of Asian Group Countries.
The park is comprised of mixed forests and rainforests with some wide plains and grasslands interspersed with verdant forests. There are many valuable plants, including commercial plants, scented plants and herbs. In addition, there are several mountains with peaks ranging from 800 to 3,000 meters above sea level making Khao Yai a cool climate area, even in summer.
The most popular time to visit Khao Yai is during the cool season or from October to February. In the rainy season, the area is refreshingly green with overflowing waterfalls, sending echoes all around.