Ramkhamhaeng's invitation to Ceylonese monks to come over and purify Buddhism in his kingdom. This Ceylonese influence manifested itself not only in matters of doctrine but also in religious architecture. The bell-shaped stupa, so familiar in Thai religious architecture, was derived from Ceylonese models. Sukhothai style Buddha images are distinctive for their elegance and stylized beauty, and Sukhothai's artists introduced the graceful form of the "walking Buddha" into Buddhist sculpture.
Sukhothai's cultural importance in Thai history also derives from the fact that the Thai script evolved into a definite form during King Ramkhamhaeng's time, taking as its models the ancient Mon and Khmer scripts. Indeed, this remarkable king is credited with having invented the Thai script.