Lying in Nakhon Sri Thammarat Province, Khao Nan National Park is a part of Krung Ching Sub-district, Noppitam Sub-district and Talingchun Sub-district, Thasalar District, and Khaonoi Sub-district, Theparat Sub-district and Plian Sub-district, Sichol District. The park consists of high mountain ranges and productive rainforest which is the source of the important rivers in the Province. There are valuable floras and wonderful natures such as Nam Tok Sunanta (Nam Tok Khao Nan), Nam Tok Krungnang, Nam Tok Klongpean,Nam Tok Kradai and Krungnang Cave etc. The park is 409.79 square kilometers.
The Park consists of complicated mountain range along north and south. The important mountains are, for examples, Khao Nan Yai, Khao Nan Mia, Khao Lek and Khao Chong Lom. Khao Nan Yai which is about 1,438 meters above sea level is the highest. The park is a part of Nakhon Sri Thammarat Mountain Range. Most of the area is productive rainforest which is the main source of the river in the area, and the habitat of many kinds of wide life, and valuable floras. There also is the rich source of minerals, for examples, tin, barite and wolfram.
Most of the area consists of productive rainforest which causes high humidity in the air and heavy continuous rain so that the weather in this area is rather cold all the year round.
90% of the area is productive rainforest which has many valuable plants such as Yang, Malacca Teak, iron wood, thingan, Heritiera sumatrana Kosterm and wild champak for example. More over, there is a special plant called Elaleriospermum tapos B1—its fruit is expensive and popular for eating, which grow together in a large cluster. The Elaleriospermum tapos B1 is rarely found growing in cluster, so its cluster in this area may have been the important supply of its seed. There also are a large number of animals, for example mountain goat, tapir, barking deer, wild boar, mouse deer, palm civet, civet and many kinds of bird, reptile and amphibian.