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.
Tropical moist evergreen forest covers the central area of Khao Yai National Park. The rich diversity of plants (about 2,000 species) astound the new-comer. Towering trees draped in mosses, climbers and epiphytes, tangled trunks of the strangling figs, drooping lianas and spiny rattan palms, delicate ferns, multicoloured lichens and an ever-changing array of fungi. There is aways something new to discover in the forest. The park has a diverse plant community, comprised of five main vegetation types:
Dry Evergreen Forests: These forests cover the lower slopes of Khao Yai. There are a number of important plant species found within this type of forest, including Dipterocarps and Hopia. Bamboo is also often found in drier forests.
Dry Deciduous Forests: These forests also cover the lower slopes of Khao Yai. The most important plant species found within Deciduous Forests include Afzelia, Xylia and Lagerstroemia.
Tropical Moist Evergreen Forest: Tropical Moist Evergreen Forest covers around 70% of the park, including its central area. Dipterocarps are an important species found within these forests.
Hill Evergreen Forests: This forest type grows above 1,000 m. In Hill Evergreen Forests, the trees are smaller and ferns, mosses and epiphytes abound. Lithocarps and Catanopsis are amongst the most important species found here.
Grasslands: These areas are a unique habitat, and provide a grazing area year – round for some of the parks animals. Grassland provides a welcome relief to all the forest . The park mange (burn annually) the grassland to prevent trees from invading and to provide year round grazing for deer, elephants and guar. Wildlife is plentiful (70 mammal species, at least 74 species of herptile and thousands of invertebrates) but often hard to see. Sambar (large, gray-brown, often in groups) and barking deer (smaller, red-brown, usually in pairs or alone) are frequently seen in the grasslands or on spotlighting tours.
Khao Yai’s forests are teeming with wildlife and birds. Look up and down and form side, tread softly, and listen carefully to discover the real movers and shakers in the forest. Gibbons provide an excellent morning wake-up call with their mournful hoots. Quiet, patient walkers may catch a glimpse of these tree-living apes. Macaques are often seen on the roadsides. Elephants are sometimes spotted at salt-licks or on the road in the evenings and lucky (?) tourists may spot a tiger in the grasslands during the evenings.
Civets, squirrels, porcupines, and wild pigs add a bit of variety. Snakes and lizards usually make their presence known by a rustle in the undergrowth as you are walking. If you see a snake, treat it as dangerous unless you know otherwise!! Geckos are frequently seen catching insects on building walls and ceilings. Cicadas never stop their scratchy hum. Look up and down and from side to side to spot the real movers and shakers in the forest - the insects and invertebrates.
Birds: We've got lots - over 320 species have been recorded. To the non-expert, birds are often just mysterious whistles, trills and calls, or a flutter of wings and a glimpse of colour. Patience is needed,good binoculars and a bird guide help. Roadsides, the old golf course, grasslands and the watching towers are good places to start . Hornbills are quite easy to spot, and hear the "gak gak gak" laugh of the Indian Pied (often seen in big flocks near Nong Pak Chi Tower in the evenings), or the deep resonant "gok…gok" of the Great Hornbill (usually seen in pairs or alone, the biggest of Khao Yai's hornbills)
Bats: Nearly 1 million insecteating bats live in a cave on the edge of the Park. Drive about 3 km to the north of the Park Chong entrance gate and take a small track on the left-hand side just past a temple. A few hundred metres up here take a right-hand turn and follow the track to the end. You can climb the hill to the cave. Please do not enter the cave - you will disturb the bats. Allow them to come out for about 3 minutes before taking any flash photography.