Located in coast of Prachuap Khiri Khan Province, it is the first marine national park of Thailand. Khao Sam Roi Yot means "The mountain with three hundred peaks" and refers to a series of limestone hills along the Gulf of Thailand with highest one at 605m above the sea level. The northwest corner of the mountain range is called Thung Sam Roi Yot and is mainly freshwater marsh covering nearly 37% of the national park which makes it the largest wetlands area in Thailand. 

The main attractions of the national park are Phraya Nakhon Cave with it's iconic royal pavilion and huge chambers, Kaeo Cave and Thung Sam Roi Yot Freshwater Marsh. The park is also an attractive destination for it's rich wildlife in mangrove forests, beautiful beaches, limestone islands, trails and view points. It is easily acessible, only 60 km south from Hua Hin and nearly 3 hours from Bangkok.

Khao Sam Roi Yot is home to a great diversity of bird species making it another great destination for birders with estimated around 300 species, half of them migratory birds. It is one of the best places in Thailand to see waterbirds on the flight path between Asia and Australia around January/February. Purple swamphen, Malayan plover, Kentish plover, white-bellied sea eagle, greater spotted eagle, oriental hobby, eastern marsh harrier, spoon-billed sandpiper are few of the birds common in the park.

The inaccessible forest areas on the mountains are home to some mammals such as dusky leaf monkey, crab-eating macaque, Malayan porcupine, mainland serow, slow loris, barking deer, fishing cat and Malayan pangolin. Dolphins are regularly seen on the coastline, although not guaranteed there is a good chance to spot some by boat trips that can be arranged form most hotels. Occationally Irrawaddy dolphins shows up near the coast.

The wild elephant watching area in nearby Kui Buri National Park is approximately 45km from the Khao Sam Roi Yot National Park headquarters, which is the best place in Thailand to see herd of elephants and gaurs. The English speaking owner of Stella Resortdoes personally drive his customers to Kui Buri National Park on availability. The impressive Pala-U Waterfalls located in south side of the Kaeng Krachan National Park is also easily accessible.

The main visitor center, headquarters and some attractions are situated on the south side of the national park. The entrance fee is 200B for adults (July 2016 price) and 100 Baht for children.