As we learned, Buddhism was first introduced to Thailand around 400 BC, when Indian traders first interacted with people living in Thailand. By the time the Dvaravati kingdom was established, Theravada Buddhism had become the most important religion in the region. The reason why Buddhism became so important is not clear, but there are some theories.
Not long after Indian traders first came to Thailand, a man named Ashoka became the leader of Indian in the 3rd century BC. Ashoka was a Buddhist and he wanted to spread the religion to other parts of the world. He sent missionaries to 9 different regions, including a place which the Indians called Suvanabhumi, which means “The Land of Gold.” We are not sure exactly where Suvarnabhumi was located, but some historians believe that it was modern day central Thailand.
This may be the reason that Theravada Buddhism became the dominant (most important) religion of the region. However, this is still a theory. Historians still do not know for sure where Suvarnabhumi was located.