The Royal Forest Department had directed the National Park Division officers to go on a field trip to carry out a survey on the area of the National Reserved Forest comprising Khlong Lam Liang-La-Un Forest, La-Un Forest Un-Pa Forest Ratchakut Forest, Khlong Set Kuat Forest, Khao Hin Chang Forest and Pa Khao Sam Laem Forest in order to classify the above National Forest Reserved area into a national park, which on 21st April, 1999, the above said area was announced as a national park called Lam Nam Kraburi National Park with the total area of approximately 160 square kilometers or 100,000 rais, comprising of 61 square kilometers or 40,000 rais of water and 99 square kilometer or 60,000 rais of land.

Topography
Lam Nam Kraburi National Park covers the area of approximately 160 square kilometers or 100,000 rais, consisting of Kraburi River, parting Thailand and Burma, to the area of 40,000 rais, small islands scattering along Kraburi River and Mangrove Forest by the Kraburi River banks covering the area of 36.5 square kilometers or approximately 15,000 rais and the National Reserved Forest area consisting of Khlong Set Kuat Forest, Khao Hin Chang Forest, Khao Sam Lam Forest,La-Un Forest Ratchakut Forest and Khlong Lam Liang-La-Un National Forest to the area of Sg.km. 45,000 rais.

Climate
The average lowest temperature in the Lam Nam Kraburi National Park is 13.7 degree Celsius and the average highest temperature is 34 degree Celsius with average rainfall at 4,276 millimeters/year. The best months and the most suitable period for tourism are between January and April.

Flora and Fauna
Vegetation
Tropical Rainforests can be found around Khlong Set Kuat Forest, Khao Hin Chang Forest, Khao Takian Forest and La-Un Forest /Ratchakut Forest National Forests and the most distinctive vegetation found only in this area is Khun Mai with large, straight trunk and cashew nut like seeds. Such vegetation is found around Punyaban Falls, La-Un Forest/Ratchakut Forest National Reserved Forest and Mangrove Forest. Other distinctive vegetations are large leaves and small leaves Mangroves, Prong, Xylocarpus moluccensis, Xylocarpus granatum, Bruguiera Sex angula, Avicennia marina, Sonneratia and Beans. Grass hills, on the other hand, cover the area of approximate 1000 rais. Such area was formerly the growing plots which were repeatedly destroyed by fire but have been revived into the existing grass hills today.
Wildlife
Mammals including Panthera tigris, Neofelis nebulosa, Asiatic black bears, mongoose, bats and civets can be found in this area while birds, for example, can be found easily around the National Park Office. As for amphibians, those which can be found around the Kraburi River are toads and frogs.
Aquatic Life
Consists of saltwater eels, carps, mackerels, mudskippers, crabs, and Kraburi River prawns.