Khao Yai National Park consists of complicated mountains such as Khao Rom, the highest about 1,351 meters, Khao Lam about 1,326 meters, Khao Keaw about 1,292 meters, Khao Sam Yod about 1,142 meters, Khao Far Pha about 1,078 meters, Khao Kampang about 875 meters, Khao Samor Poon about 805 meters and Khao Kaew about 802 meters above sea level. Moreover, the area has vastly grassy field alternating with productive forest. The north and the east part are smoothly sloping down, while the south and the west part are rising up. The area is the source of five main rivers as follows.
1) Prachin Buri River
2) Nakhon Nayok River situated in the south part and important for local agriculture and economy, meet each other in Chachoengsao District to become Bangpakong River go to the Gulf of Thailand.
3) Lam Ta Kong River
4) Praplerng River, in the north part, go to maintain the agriculture of Korat Plateau and meet Moon River, the main river of Southern Isan that goes to Khong River.
5) Muag Lek Stream, located in the northwest part and going to Pasak River in Muag Lek District, is valuable for local agriculture and cattle, and has water all the year round.