Khao Sok National Park is located on the mountain ridge which separates the east and west coasts of the Thai peninsula. It is situated in the west of Surattani province, in Ban Ta Khun and Phanom districts. Established in 1980, Khao Sok National Park was the 22nd park to be designated out of the 77 Thai National Parks. It covers an area of 738.74 square kilometers.
Originally the north side of the park was bounded by the Pasaeng River. However, since the construction of Rachabrapah Dam in 1982, and the formation of the artificial lake, the boundary of the park has been extended to include the reservoir. The reservoir itself covers an area of 165 square kilometers.
Beyond the lake extend the wildlife sanctuaries of Khlong Saeng and Khlong Nakha, and Kaeng Krung National Park. To the west of Khao Sok lies Sri Phang Nga National Park. Lying astride the junction of the provinces of Ranong, Phang Nga and Surattani these reserves make up the largest area of continuous forest preserve in the Thai peninsula at 4,000 square kilometers. It is really only in this area that large mammals such as tigers and elephants have survived in the south of Thailand, although little is known about their status

Khao Sok National Park Forest Types

Khao Sok National Park contains 3 distinct forest types. 

1. Rain Forest (Tropical Evergreen Forest)
This is the principal forest types covering the majority of the national park area. These forest are dense and stratified structures dominated by tall emergent trees, often supported by buttress roots. A large proportion of such trees belong to the Dipterocarpaceae family, easily recognized by their two winged fruits. The middle storey of the forest is an aerial tangle of figs and lianas (woody climbers). Below is the dense understorey where evergreen ground flora such as bamboo, rattan, ferns and palms compete for light.
2. Limestone forest 
This occurs on the step limestone karst scattered across the park. The various species growing in this environment can survive without very much water, their roots are able to grip into small cracks in the rock. Of particular interest is Mayburretia Furtadoana (Maak pralatoo) a small palm species endemic to Khao Sok National Park and surrounding areas
3. Secondary or Disturbed Forest. This occurs in areas which have, in the past been logged or disturbed by human activity, The vegetation growing here is characterized by invasive and fast growing tobust plan species. In Khao Sok National Park this forest type is found around the banks of the Rachabrapah Dam and lake
3. Cave.
Cave are formed by underground water and are characteristic of limestone landscapes. Khao sok National Park. Has many limestone cave, such as 'Kangkow' cave, 'Namtaloo' cave, 'Seeroo" cave. There cave have formed through a chemical process cailed carbonation in which the calcium carbonate of the limestone is dissolved by water containing carbondioxide. The rock is gradually eroded. Small cracks from enlarging more and more until a tunnel is created.
Under certain conditions the process is reversed and calcium carbonate can deposited within the cave, in the form of stalactites and Stalagmites
Stalactites are limestone "icicles' that hang down from the cave ceiling. They are formed as water drips down from cracks. As the water enters the cave, the carbon dioxide from some of the molecules diffuses out into the air and the remaining calcite crystals cling to the formation. As the water continues to flow down the stalactite, calcite crystals are deposited along the outer surface and on the tip, enlarging the formation. Water that does not lose its 

Wildlife
The richness of the tropical forest flora, the abundance of fresh water, and the shelter of the mountains all provide excellent habitats for many wildlife species. Khao Sok National Park makes up part of the largest continuous forest area remaining in the Thai peninsula. This provides the only viable habitat in southern Thailand for large mammals needing extensive areas of undisturbed forest for their survival.
Mammals.
Elephant, tiger, gaur, and banteng are known to be present. Tracks are seen regularly, although actual sightings are very rare. The status of these animals is therefore still uncertain.
Many smaller mammals are frequently encountered such as monkeys, langur, wild boar, and deer. The call of gibbons is often heard along the forest trails. 
Birds.
188 species of birds have so far been recorded in khao Sok National Park. The most spectacular. And distinctive to rainforest environments are the hornbills. There are five confirmed hornbill. The argus pheasant, another rare bird, has also been seen in the forest. 
Reptiles and Amphibia.
Very little research has been carried out to determine what species of reptiles and amphibia inhabit this area, despite the obvious abundance of these creatures, including many varieties of snakes, lizard, frogs and tortoises.
Insects
Thailand's species geographical position makes it uniquely rich in insect life. There are literally thousands of different insect species in Khao Sok: ants, beetles, butterflies, stick insects, dragonflies, and spiders. Insects play a vital role in the breakdown of matter, decomposition on the forest floor and pollination, which are all critical to the forest life cycle. Without these decomposers, life in the forest would eventually grind to a halt for lack of available nutrients. 

Attractions

You will need to trek through the wonderful moist evergreen forest to reach most of these attractions. Ask at the Headquarters for a guide and more detailed information about the treks.

                - Wang Hin Waterfall is an attractive waterfall on Klong Sok River. Huge boulders litter at the stream about 20m from the base of the falls. You can use these boulders as stepping stones to cross the river. The attractive crossing point is known locally as 'Bang Wang Hin' or Narrow Running Rocks. The waterfall is about 205 Km from the Headquarters.

                - Tang - Nam is a natural gorge created by the Klong Sok River carving a mountain in two. The steep cliff faces plunge down to the gushing stream. Walk downstream from Wang Hin Waterfall to reach this beautiful spot.

                - Ton Gloy Waterfall  water pours down this single level waterfall in a gushing torrent most of the year. Large flat boulders at the base of the waterfall provide excellent seats for weary travelers. Ton Gloy is 9 Km from the Headquarter.

                - Ton Sai Waterfall  this beautiful waterfall has many large boulders strewn around its base. Walk 2 Km downstream from Ton Gloy waterfall to reach it.

                - Trarnsawan Waterfall  is a beautiful waterfall tumbling down a limestone cliff - face. It is about 3 Km walk downstream from Tang-Nam.

                - Sib-Ed Chan Waterfall water pours over the 11-stepped staircase of rocks that makes up this attractive waterfall. The large pool at the bottom is great for swimming - you will need cooling down after walking the 4Km from Headquarters!

                - Mae Yai ( Grandmother ) Waterfall this waterfall is the most accessible as it is close to the Surat Thanee to Dagua Baa road at Km 113 - even your grandmother can get there! The 30m high waterfall is very beautiful.

- Bat Cave  Thousands of bats live in this large chambered cave. You can hear them twittering and squeaking and will smell  their distinctive aroma as you explore the cave with its beautiful stalactites and stalagmites. Please do not shine torches up onto the bats, as these will disturb them, as will loud noise.

- Cheow Lan Dam This large man-made dam was built to provide hydro- electricity for Surat Thani and other wowns. Over 100 islands dot this massive lake, most of the clustered in the narrowest part of the lake, an area known as ' Chong Kaeb Khao Ka Loh' The dam is a 50 Km drive from eadquarters. Local people run boat trips and trekking around the Dam as part of an eco-tourism project.