There is a northern Thai story that tells how the naga—a mythical serpent—came and destroyed the town known as Yonok (c. thirteenth century) after its ruler became immoral. Despite this divine retribution, the people of the town chose to rebuild it. Many archaeological sites indicate resettlement during this early historical period. Although many temple sites were constructed in accordance with the Buddhist cosmology, the building patterns vary from location to location and illustrate what this paper calls ‘nonconventional patterns,’ distinct from Theravada Buddhist concepts. These nonconventional patterns of temples seem to have been widely practiced in many early historical settlements, e.g., Yonok (what is now Wiang Nong Lom). Many local written documents and practices today reflect the influence of the naga myth on building construction. This paper will demonstrate that local communities in the Chiang Saen basin not only believe in the naga myth but have also applied the myth as a tool to interact with the surrounding landscapes. The myth is seen as a crucial, communicated element used by the local people to modify and construct physical landscapes, meaning Theravada Buddhist cosmology alone cannot explain the nonconventional patterns. As such, comprehending the role of the naga myth enables us to understand how local people, past and present, have perceived the myth as a source of knowledge to convey their communal spaces within larger cosmological concepts in order to maintain local customs and legitimise their social space.