An interesting thing about the Sukhothai historical area is the mix of styles. Usually it's a temple of one style over here, another style over there, but in Wat Mahatat, the biggest temple of the complex, it's every style that was available all at once. Stylistic elements from Ceylon, India, Thailand, Lanna (an ancient Thai kingdom in the North), and the Khmer all are present in the one temple.
Elements of many religions too. Buddhism, of course, plus Hindu, plus the Linga/Yoni stuff that predated Hinduism in India. It's pretty wild.