Khao Sam Roi Yot National Park (, ) is a marine national park in Kui Buri District, Prachuap Khiri Khan Province, Thailand. It covers 61,300 rai ~ of which 13,050 rai ~ are marine areas. The park was established in 1966, and was the first coastal national park of Thailand. The park includes Thailand's largest freshwater marsh. Geography The limestone hills are a sub-range of the Tenasserim Hills that arise at the shore of the Gulf of Thailand, with the highest elevation being Khao Krachom at . Between the hills are freshwater marshes. Several of these marshes were converted into shrimp farms, as only 22,000 rai ~ of the total 43,000 rai ~ of marshes are part of the national park. A portion, 11,000 rai ~ , of these marshes are scheduled to be declared a Ramsar site. Two white sand beaches are in the park, Hat Laem Sala and Hat Sam Phraya. Hat Laem Sala is 17 km from park 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. Five uninhabited islands lie just offshore. The park is approximately south of Hua Hin. The origin of the name "Khao Sam Roi Yot" is undetermined. Local lore has it that it means 'mountain with 300 peaks', or the range had been an island where 300 survivors from a sinking Chinese junk sought refuge, or the range was named after a local plant called sam roi yot. Phraya Nakhon Cave Phraya Nakhon Cave () is about from Laem Sala Beach, approximately north of park headquarters. Visitors can go to the cave by renting a boat or by walking across Tian Mountain. After that, there is a climb up the mountain about to reach Phraya Nakhon Cave. Its most famous early visitor was King Chulalongkorn. There is a water well at the foot of the mountain known as Phraya Nakhon Well. It is made of baked clay bricks in a trapezoidal shape. Phraya Nakhon is a large cave which has a hole in the ceiling allowing sunlight to penetrate. At the top of the hole, there is a stone bridge known as "death bridge" because many wild animals have fallen to their deaths from it. Khuha Kharuehat Pavilion () is a historic site built for King Chulalongkorn's visit to the region in 1890. At certain