Ancient Khmer Cultural Influences in the Mun River Basin: A Case Study of Sung Noen District, Nakhon Ratchasima

Sung Noen District in Nakhon Ratchasima Province constitutes one of the most significant archaeological landscapes in the upper Mun River Basin, reflecting the long-term cultural, religious and sociopolitical transformation of ancient communities from the Dvaravati period (7th–10th centuries CE) to the era of Khmer influence (11th–13th centuries CE). The area encompasses key archaeological remains, including the ancient city of Sema, the early polity of Srijanasa, sandstone sanctuaries and the monumental reclining Buddha at Wat Thammajak Semaram, recognized as the oldest outdoor sandstone reclining Buddha in Thailand. This article examines the process of cultural transition and integration between indigenous Dvaravati traditions and the expanding influence of the Khmer Empire through an interdisciplinary approach incorporating historical, archaeological and art-historical analysis. It highlights Sung Noen as a critical civilizational frontier where religious ideologies, architectural forms and systems of sacred power converged, ultimately shaping a distinctive regional identity. The study further demonstrates how this transformation contributed to the formation of the spiritual landscape and long-term cultural continuity of Northeastern Thailand within the broader context of early Southeast Asian civilization.