During the Dvaravati period (seventh through eleventh centuries), there were two factions of Buddhism practiced in the region that now encompasses present day Thailand, namely Mahayana and Theravada.
Typically, they reflect the teachings of the Mahayana school of Buddhism, which often emphasized the veneration of the sacred figure of Boddhisattvas.
In 1905 Prince Damrong Rajanubhab removed the statue from Wat Wiang, Chaiya, Surat Thani to Bangkok National Museum, Thailand.
They are typically found in Northeast Thailand, and their style is essentially similar to Cambodian Buddha images.
During the Sukhothai period (fourteenth century), the style of the Thai Buddha images radically changed due to the influx of new ideas from Sri Lankan Buddhism.
The Sukhothai period witnessed the innovation of the four modern postures of the Thai Buddha, i.e. walking, standing, sitting and reclining.
Images often had a flame-shaped aureole, finely curled hair, a slight smile, broad shoulders and an oval face.
Wat Traimit Golden Buddha, which is a famous tourist attraction in Bangkok, is made in the Sukhothai style, so it may indeed date from that period.
Bunleua Sulilat's concrete sculpture gardens (Buddha Park and Sala Keoku) give an example of contemporary highly creative and unconventional artistic treatment of Buddhist subjects.