The lake did not exist before 1982. Ratchaprapha Dam, built across the Phra Saeng River for hydroelectric power, flooded 165 square kilometres of forested valley floor and left only the summits above water. What appears to be an ancient seascape of karst islands is in fact a drowned mountain range, barely four decades old. The limestone itself is far older. These towers are the eroded remnants of a Permian reef complex laid down some 250 million years ago, when the region lay beneath a shallow tropical sea. Rainfall dissolved the softer rock over millennia, leaving vertical pinnacles and cave systems. The tallest formations near Khao Sam Kloe rise more than 900 metres above the waterline. Local guides call the cluster Guilin of Thailand, after the Chinese karst landscape it resembles. Khao Sok National Park was gazetted in 1980, two years before the dam closed its gates. The surrounding rainforest is frequently described as older than the Amazon, a claim resting on its position within an unbroken evergreen belt that escaped the last ice age. It shelters Rafflesia kerrii, the parasitic flower that blooms up to 80 centimetres across, along with hornbills, gibbons, langurs and a small resident population of Asian elephants. A cheow lan lake tour overnight remains the only practical way to reach the park's remote northern arms, where road access ends and water begins. The raft houses came later. Villages displaced by the flooding were resettled, and fishing families began mooring simple bamboo platforms in the sheltered coves. Those platforms evolved into the floating bungalow accommodation now anchored at Klong Ka, Ton Toey and Nang Prai. Construction remains deliberately light: timber decking, thatch or corrugated roofing, tethered to shore by cable rather than piling. Nothing touches the lakebed. Access runs through the pier at Ratchaprapha Dam, Khao Phang, Ban Ta Khun District, Surat Thani 84230, Thailand, where the national park entrance fee of 300 THB per foreign adult is collected. Khao Sok National Park tours departing from Khao Lak, Phuket and Khao Sok village all converge here. Beyond the dam wall, engine noise gives way to the flat sound of water against hull, and Nam Talu cave, the Coral Cave and the wildlife channels open one after another. The park has become a case study in how infrastructure can accidentally create a landscape. Whether reached by shared longtail or a private charter, a cheow lan lake tour overnight delivers visitors into a reservoir that behaves, entirely convincingly, like wilderness.