Initially, Lan Hin Ngam was known by local villager. However, in 1985 (B.E. 2528), when Thep Sathit District Officer and Thep Sathit District Forest Officer surveyed and discovered of natural rock garden, which was very beautiful. They thought it should be conserved for tourism and recreation. Therefore, they presented document to the Royal Forest Department in order to set a national park. On the 10th October 1986 (B.E. 2529) this area was declared as Pa Hin Ngam Forest Park, with the area of 10km2.
In 1993 (B.E. 2536), the Royal Forest Department surveyed the area near by and found that 80km2 of surrounding forest is still fertilizing. Therefore, due to its fertile forest and fascinating features, this Forest Park was designated a national park on the 19th September 1994 (B.E. 2537).
The area consists of mountain range which has mountains, such as Pung Haui Mountain, about 200-800 meters above sea level. In geology class, the area divides into Phupan Rock, Prawihan Rock and Phu Kradaung Rock which are the rock, about 180-230 million years ago, of Jurassic and Triassic era. Also, the area is the source of water of She Riverís area and Sonthi River which empty into Parsak River.
The forest is semi-evergreen forest mixed with deciduous forest. The main plants are Siamese sal, ingyin, Burmese ebony, Lithocarpus collettii A. Camus, Payom (a kind of Dipterocarpaceae), pride of India, San (a kind of Dilleniaceae) etc.
Animals found are barking deer, wild boar, hare, pangolin, porcupine, bamboo rat, palm civet, squirrel, monkey etc.