The Khun Yuam Document is a historical record found in Thailand that provides details about the construction of an irrigation system in the Khun Yuam district in the late 15th century. It describes how a local leader named Khun Pha Muang organized villagers and laborers to dig canals and build weirs and dams to provide water for farming lands during the dry season. The system helped increase agricultural production and brought prosperity to the local communities in Khun Yuam.