Kaeng Krachan was declared as a national park on 12 June 1981. Covering an area of 2914 km² it is the largest national park in Thailand. The park is located in Phetchaburi and Prachuap Khiri Khan Provinces, bounded by the Tanintharyi Nature Reserve along Myanmar's border to the west. The park is not only part of the rainforest area north and south of the park in Thailand, but also part of the Western Forex Complex that covers 18,730 km² across 19 protected sites between Myanmar and Thailand.
Kaeng Krachan National Park is famous it's diverse wildlife, but also for the dense morning mist covering the park with hill tops sticking above mist cloud around December-March, creating a spectacular view.
Two main rivers, Phetchaburi and Pran Buri Rivers are both originated from Tanaosri Ranges within the park. At the north side of the park, water streams drains to the Phetchaburi River which flows to Kaeng Krachan dam and flows all the way to Gulf of Thailand though Phetchaburi Province. At the south side the water streams drains to the Pranburi River, which too flows into a dam in Pranburi Province and finally to Gulf of Thailand.
Kaeng Krachan National Park covers a reservoir and mainly rain forests with rich flora and fauna. The highest elevation is a peak along the Burmese border at around 1500 meters. The second highest peak is Khao Phanoen Thung at 1,207 meters used to be accessible by an overnight trekking from Phonoen Thung Camp Site but this trail is closed since 2014 (still is as of Feb 2016, there are no plans to open it anytime soon).