Siliceous sandstones used in Khmer temples such as the Prasat Basset, Wat Ek Phnom, and Phnom Banan temples in Battambang Province, Phnom Chisor and Ta Prohm temples in Ta Keo Province, and Wat Nokor Bachey temple in Kampong Cham Province in Cambodia were investigated in this study to determine the supply source of the siliceous sandstones used in these temples. Chemical composition analyses and magnetic susceptibility measurements were conducted for the sandstone blocks used in these temples. Siliceous sandstone is the primary construction material in the investigated temples, except for the Phnon Chisor (bricks). Two types of siliceous sandstone, pale brown and red, were found. Pale brown siliceous sandstone was used for the construction of all the investigated temples. In contrast, red siliceous sandstone was found only in the Wat Ek Phnom, Prasat Basset, and Phnom Banan temples. It is suggested that the pale brown siliceous sandstone originated from the Phra Wihan Formation within the Khorat Group. Based on the chemical composition analysis, the pale brown siliceous sandstone in the Ta Prohm temple at Tonle Bati and the Wat Nokor Bachey temple may have been sourced from the lower level of the Phra Wihan Formation. In contrast, the pale brown siliceous sandstone used in the Prasat Basset, Wat Ek Phnom, Phnom Banan, and Phnom Chisor temples was likely sourced from the upper level. The origin of the red siliceous sandstone is proposed to be from the Sao Khua Formation, which is situated above the Phra Wihan Formation.