Chronology : Mr.Surachat Chamnansin, the village headman of Na Yung sub–district, Nam Som district, Udonthani Province offered a document on October 25, 1975 to the Royal Forest Department in co-operation with Mr.Sanong Chatwethin who is the head of Forest Protection Station (Unit 2) and with Mr.Manat Techasathian, forest officer had surveyed the forest area in Na Yung sub-district, which is on the boundary of Phu Phan mountain range, found the general condition similar as wildlife sanctuary protection in Chon Buri Province. It is specific outstanding on the mountain ridge of Na Yung District that is beautiful and the waterfall is much more beautiful, proper improvement to be a relaxing place. So the Royal Forest Department sent some officers to surveyed that information, occurred this Nayung forest is in the boundary of a kind of interior wood Nayung project forest (unit 25) section 10, Namsom district, Udonthani province and it never had had forestation before, proper improvement to be a relaxing place in the pattern of the Forest Park. So Royal Forest Department declared to be a forest park on December 26,2518, in the responsibility of Udonthani Province Forest Office.
Later that Royal Forest Department received a report from Natural Resourecs Conservation Office ÇèÒ Na Yung-Nam Som Forest park and nearly forest area which is some parts of conservation forest of Pa Phran Phrao – Kaeng Kai, Pa Phukhao Kaeo – Dong Pakchom and Pa Na Yung – Nam Som National Reserves Forests, Udonthani Province with total area about 344 sq.km, abundant forest condition and beautiful natural, appropriate to be a national park. So the Royal Forest Department had the order number 736/2544 to Mr. Dechavut Sethapun, who is the head of Phu Pha Lek National Park and the head of Na Yung-Nam Som Forest park surveyed the primary information.
Later that National Park, Wildlife and Plant Conservation Department had the order number 326/2547 on February 19, 2004 to Mr. Phitsanu Wongkasem, forest officer , the head of Phu Phra Bat Buabok Forest Park and the head of Na Yung- Nam Som Forest Park administered Na Yung-Nam Som National park.
Na Yung-Nam Som National Park is the 3 patched-province area:Udonthani, Loei and Nongkhai, The topography condition is slope complex mountainous above 200-500 m from msl, the mountain with the highest peak is Phu Ya-u about 588 m. General forest condition is still maintain the abundance where it is the main source of the river and the stream, such as Huai Nam Som, Huai Tat Ton.
The monsoon, very hot weather in the summer about 40oC between March to May. Rainy season runs in June to October and a winter about 10-20oC, rain amount all year about 1,000-1,500 ml.
Forest condition is dry dipterocarp forest, distribute along foothills and hill range. The main species are Shorea obtasa, S. siamensis, Dipterocarpus tuberculatus etc. Lower plants are Vietnamosasa pusilla, Curcuma sp. Down the valley is mixed deciduous forest, found Dalbergia oliveri, Xylia xylocarpa, Pterocarpus macrocarpus, Sindora siamensis, and various species of bamboo such as Gigantochloa albocilliata, Bambusa bambos, Dendrocalamus sp.. Along the riverside is dry evergreen forest, found Afzelia xylocarpa Anisoptera costata, , Dipterocarpus spp. Lagerstoemia spp., Hopea sp. etc. Lower plant found rattan, palm, herbs etc, while symbiosis species found orchid and fern.
Fauna found wild boar, common muntjac, macaque, langur,squirrel, clouded monitor, snakes and birds. For large sized wildlife found sambar deer, Indian elephant, Asiatic black bear but they were hunted seriously, also with remained wildlife was threaten and hunted by the people in the area.