This article examines the Lam Takhong waterwheel (rahad) in Nakhon Ratchasima as a surviving example of vernacular irrigation technology reflecting the trans-civilizational transfer of hydraulic knowledge from Mesopotamia and China to Siam. Adapted to the environmental conditions of the Korat Plateau, the rahad represents an appropriate technology integrating engineering knowledge, local materials and community practices. In 2025 (B.E. 2568), the Lam Takhong waterwheel was inscribed on Thailand’s National Intangible Cultural Heritage list by the Department of Cultural Promotion, Ministry of Culture, under the category of heritage requiring urgent safeguarding. The Lam Takhong rahad thus stands as both a historical testimony of global irrigation technology and a vital local cultural heritage that reflects the relationship between technology, environment and agrarian life in Thailand.