The name Khao Sam Roi Yot translated from Thai describes the Mountains with 300 peaks, which describes the surrounding area precisely. The jagged limestone peaks rise directly at the shore of the Gulf of Thailand, with the highest point being Khao Krachom which is 605m above sea level. Between the hills are freshwater marshes which provide habitat for many unique species of birds and wildlife.
Two white sand beaches are located within the park namely Hat Laem Sala and Hat Sam Phraya. Hat Laem Sala is 17 km from the park’s headquarters and can be reached from the village Ban Pu either by boat or by climbing up and down over a hill for nearly 30 minutes.
Rare animals in the park include the Mainland Serow, Dusky Langurs, as well as many bird species. Irrawaddy Dolphins can occasionally be seen in the ocean, which give the name to Dolphin Bay.
The area of the Khao Sam Roi Yot is likely to be the site where King Mongkut (Rama IV) convened with European guests on August 18, 1868 to observe a total solar eclipse. The king was very interested in astronomy and had calculated the date and location of the eclipse himself. It is unfortunate that he contracted malaria during that event, and died shortly later
Later kings also visited the area, especially the Phraya Nakhon cave. The cave consists of two caverns, illuminated by their collapsed roofs. For the visit of King Chulalongkorn (Rama V) in 1890 the Kuha Karuhas pavillon was built inside the cave. Later King Vajiravudh (Rama VI) as well as the current king Bhumibol Adulyadej (Rama IX) visited the cave.
The national park was created on June 28, 1966. It was enlarged on April 1, 1982.