I. Theravada or Southern Buddhism
That the first form of Buddhism introduced to Thailand was that of Theravada (The Doctrine of the Elders) School is proved by various archaeological remains unearthed in the excavations at Nakon Pathom, such as the Dharma Chakra (Wheel of Law), the Buddha footprints and seats, and the inscriptions in the Pali language, all of which are in rocks. Such objects of Buddhistic veneration existed in India before the introduction of the Buddha image, which appeared later as a result of Greek influence. Buddhism, therefore, must have reached Thailand during the 3rd century B.C., and it must have been more or less the same form of Buddhism as was propagated by the great Buddhist Emperor Asoka. This form of Buddhism was known as Theravada or Hinayana (The Lower Vehicle) in contradistinction to the term Mahayana (The Higher Vehicle); the two schools having sprung up soon after the passing away of the Buddha. When worship of the Buddha image became popular in India, it also spread to other countries where Buddhism had already been introduced. This is borne out by the fact that many Buddha images, especially those of the Gupta style, had been found in the ruins of Nakon Pathom and the neighboring cities. Judging from the style of the Buddha images found, it can also be assumed that the early Buddhist missionaries to Thailand went from Magadha (in Bihar state, India).