Previously known as Lake Chiew Lan, His Majesty King Bhumibol Adulyadej was responsible for naming the dam Ratchaprapha ('Light of the kingdom'). Located at Ban Chiew Lan in Khao Pang sub-district, construction of the dam was completed in 1988. Covering 165 square kilometers of Surat Thani province, the reservoir area includes over 200 islands within its boundaries and is part of a forest center overseen by Khao Sok National Park.