Ku Mahathat is a Bayon-style Khmer sanctuary believed to have been constructed in the late 13th century during the reign of Jayavarman VII. It served as an “Arogyasala,” or ancient hospital sanctuary, established to provide medical treatment and spiritual healing according to the Mahayana Buddhist beliefs of the Khmer Empire. The term “Arogyasala” comes from Sanskrit, meaning “a place free from disease,” reflecting one of the earliest organized public healthcare systems in Southeast Asia.

The sanctuary was primarily built from laterite stone and features a square-shaped main prang tower with its only real entrance facing east, while the other three sides contain false doors in traditional Khmer architectural style. Inside, it is believed to have once housed an image of Bhaishajyaguru Vaiduryaprabha, the Buddha of Medicine. Nearby stands a bannalai, or library building, used for storing scriptures and medicinal herbs. The complex is enclosed by laterite walls and surrounded by a baray, an ancient reservoir used for both ritual and practical purposes.

One of the site’s most notable features is the carved lintel depicting Vishnu riding Garuda in Bayon artistic style. The original lintel is now preserved at Khon Kaen National Museum, while a replica has been installed at the sanctuary. The intricate carvings reflect the refined craftsmanship of late Khmer artisans, characterized by delicate and flowing decorative patterns.

Ku Mahathat is archaeologically significant as evidence of the expansion of Khmer influence into the Chi River basin and as a reflection of ancient healthcare systems, religious beliefs, and Khmer cultural heritage in Northeastern Thailand. Today, the sanctuary has been restored by Thailand’s Fine Arts Department and stands as one of Maha Sarakham’s important historical attractions, surrounded by peaceful greenery within the grounds of Wat Ku Ban Khwao.