This stunning 165-sq-km lake sits 65km (an hour’s drive) east of park headquarters. It was created in 1982 by an enormous shale-clay dam called Ratchaprapha (Kheuan Ratchaprapha or Chiaw Lan). Limestone outcrops protruding from the lake reach up to 960m, over three times higher than Phang-Nga's formations. Most lake visits involve a day or overnight tour (including transfers, boats and guides).
Charter boats (per day 2000B) from local fishermen at the dam's entrance to explore the coves, canals, caves and cul-de-sacs along the lakeshore.
Two caves can be accessed by foot from the southwestern shore. Tham Nam Thalu , contains striking limestone formations and subterranean streams. Visiting during the rainy season isn't recommended; there have been fatalities. Tham Si Ru features four converging passageways used as a hideout by communist insurgents between 1975 and 1982.
