Formerly, Nam Tok Ngao National Park was called Klong Prao National Park, located in Amphur La-un, Muang, Ranong province; and Amphur Sawee, Thung Tago, Lung Suan, Pa To, Choomporn province. At 668 km2, the park's general geography is rugged mountain range. And it has valuable trees forest and headwaters, suit to set a national park.
The general topographic composition of the park are mountainous regions, which includes Khao Daen, Khao Huai Siat, Khao Nom Sao, and can be seen stretching from the northern to southern areas of the land. Khao Nom Sao is not only the highest mountain in the park, peaking at a height of 1,089m above sea level; it also provides a very important watershed for the provinces of Ranong and Chumphon.
Due to the monsoons experienced in Thailand during the months of May till December, January through to April is considered the best time to visit Nam Tok Ngao National Park.
There is moist evergreen forest with valuable floras some are Podocarpus neriilolius, Hopea odorata and Michelia champaca. Beside, there is an orchid scattered in deep forest -Dendrobium Formosum, which is similar to Cathalia Orchid and bloom from October to December. Bour Put (Reffesia Kereii Mejjer) Itís a new species of fauna and the largest flower in the world. Actually, itís parasitic species in the Rafflesia. Itís remarkable, not only because of their size, but also because the flower is the only part of the plant that is visible which appeared on the ground, only in rainy season. Its characteristic is similar to dark red cabbages.
Wildlife existing in the park includes wild elephants, tapirs, gaurs, leopards, bears, barking deer, monkeys, langurs, wild boars, serows, cobras, King cobra, python, jungle fowl, hornbill, etc. The most important of all the wildlife species found in the park is the famous Chao Fa crab (Phricotelphusa sirindorn Naiyanets) which was discovered around
the Nomtok Ngao National Park area of the Ranong province.