In the past this national park is only the sea shore forest park of Khao Lak, until Mr. Somchit Suksanga, village chief of Mu 3, Kapong sub-district, Kapong, Phang Nga, had proposed to the assistant minister of agricultural and cooperative on september 26, 1984 for considering to declare the forest of Amphoe Ka Pong and nearby forest to be the conservation forest for conserving the origin or source of water of Phang Nga province which still be the perfect forest and has a lot of wild animals. Morever, this area still has a colorful tourist attraction, especially many small waterfalls. This area became the 66th national park on August 30, 1991 namely "Khao Lak -Lam Ru Natitonal Park covers 125 squarekilometre
General geograhy consists of many moutains such as Lak mountain, Lam Ru mountain, Sang Tong mountain, Mai Kaeo mountain and Prai Bang Toa mountain. The highest peak is about 1,077 meters about the sea level which is the origin of the important rivers of Phang Nga province, namely Ta Kua Pa river and Phang Nga river and also consisting of many small canals and streams. The Khao Lak - Lam Ru national park office is located in the shore area nearby sea covering the rock beach ecological system, sand beach and coral ecological system.
The Khao Lak - Lam Ru national park is located in the western coast of Andaman sea, let it get an influence of southwestern monsoon wind and northeastern monsoon wind which induce to have raining for almost all year round. It's two seasons, hot season starting from January till April and raining season starting from May till December which would have a lot of rainfall.
The majority of the park is covered by Tropical evergreen forest, some is still pristine, whereas in other areas human encroachment has altered the forest structure. In some places the original forest has been completely replaced by fruit trees or rubber plantations. The park also has some small areas of coastal habitat and small secluded sandy beaches.
Tropical evergreen forest, this occurs on the forested hills of Khao Lak. In places with little human disturbance this forest is highly differentiated with; a ground flora, an undergrowth of seedlings, then a canopy of three levels, lower, intermediate and upper and above this a few emergent forest giants. The principle tree species recorded include; Dipterocarpus sp., Alstonia scolaris, Anisoptera costata, Michelia champaca, Syzygium sp., Hopea odorata, Mimusops elengi, several palm (Palmae) species and Bamboo (Gramineae). This forest is also very rich in epiphytes such as Orchids and ferns, and snaking between the trees are Lianes and many climbers including Rattans.
In small patches near the coast the forest includes many marine tolerant species including; Barringtonia asiatica, Anacardium occidentale and Pandanus odoratissimus.
Mammal animals consists of Colugo, Binturong, Malaysian weasel, Drynaria. bonii H. Christ, Bat and the big mammal animals found here are. Sumatran serow, Malayan Tapir, etc.
Retiles could be classified into the daytime living reptiles such as Idian or Bengal Monitor, etc. and the reptiles that you could find directly are Snake such as Iridescent earth snake, Malayan pit viper, and White-lipped pit viper.
Amphibians such as Bufo asper Gravenhorst, Rana laticeps Boulenger, and Heymon's Froglet, etc.
Birds, from survey could be classified into 15 class-orders 108 families, for example Crested serpent-eagle, White-bellied sea-eagle, Emerald Dove and Scarlet Minivet , etc. while the big birds could be found 3 types, namely Bushy-crest hornbill, Oriental pied hornbill, and Homrai.
Daytime butterflies, most of them could be found in the primary rainforest, especially in the creek or pond area. The daytime butterflies are defined as conserved animals totally 3 types, namely Troides aeacus thomsoni, Troides amphrysus ruficollis, and Stichophthalma godfreyi.
Sea animals , for example the sea cucumber group such as Black Cucumber, H. scabra, etc. , the hedgehog group such as Malayan Porcupine, etc., the sea slug such as Feather star, etc., the fish group such as Morey eel, Lizardfish, Long Tom, etc., the star group such as Feather star, the crab group such as Giant murex, Tiger Cowrie.