Mostly the National Park Thung Luang Salaeng an area of ​​1262 square kilometers, consists of limestone hills in height from 300 to 1028 meters above sea level. Here, however, there are also plain. In the park is the river Wang Thong. Most of the hills covered with deciduous and mixed deciduous forests, rarer tropical evergreens and meadows.

The proposal to include Thung Luang Salaeng list of national parks in Thailand arrived in 1959, it was realized only in 1972. Since the late 50's to early 70's forest park were used as the main locations of the guerrillas of the Communist Party of Thailand.

The national park is amazingly beautiful three-tiered waterfall Kaeng Song (or Namtok Kaeng Sopha). It is the largest in the province of Phitsanulok, has been dubbed the "Niagara" by analogy with the world's largest waterfall. In June 2007, Kaeng Sopha image was released on a postage stamp in a series of "Waterfalls of Thailand."

The fauna of the national park is rich and diverse. It is home to elephant, palm civet, yellow marten and more than 160 species of birds. The most valuable of these is the rare Siamese Pheasant.

Thung Luang Salaeng particularly beautiful from November to December, during this period of wild meadow flowers bloom, which in turn attract local fauna. The most beautiful and popular destination at this time is plain Thung Non Son.