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
Khao Yai has three main seasons, with an annual mean temperature of 23 ° C, though this varies greatly with the seasons.
Rainy Season: May-October. During this season, it rains most days, resulting in stunning waterfalls. The atmosphere is humid, with average daytime temperatures of 27° C, In the humidity, flora and fauna flourish, whilst after the rain there is clean air and clear visibility (great for photograph!).
Cold season: November- February. This is the most popular time to visit Khao Yai, as clear, sunny and cool weather are ideal for hiking and nice sunsets are common. The days average around 22° C, while the nights can drop to 10° C.
Hot Season: March-April Even in the hot season, Khao Yai does not experience of heat felt elsewhere in the country. Daytime temperatures reach between a high 20° C, to a low 30° C, During this season it is dry and often windy. Waterfalls can be dry by April.