Buddhism first appeared in Thailand during the 3rd century B.C. in the area of the present day provincial capital Nakhon Pathom. Once established, it proved such a durable and pervasive force that some ethnic groups who migrated into that area during the Dvaravati period readily adopted it as their state religion.
Briefly, Buddhism teaches that one's life does not begin with birth and end with death but is a link in a chain of lives, each conditioned by volitional acts (karma) committed in previous existences. The concept of karma, the law of cause and effect, suggests that selfishness and craving result in suffering. Conversely, compassion and love bring happiness and well-being. Therefore, only by eliminating desire can one find peace of mind. The ideal Buddhist aspiration is to attain perfection through Nirvana (Nibbhana), an indescribable, immutable state unconditioned by desire, suffering, or further rebirth, in which a person simply is, yet is completely at on with his surroundings.
After its introduction into Thailand, Buddhism gained wide acceptance because its emphasis on tolerance and individual initiative complemented the Thai's cherished sense of inner freedom. Fundamentally, Buddhism is an empirical way of life. Free of dogma, it is a flexible moral, ethical, and philosophical framework within which people find room to fashion their own salvation.
Sukhothai's King Ramkhamhaeng (1275-1317 A.D.) established Theravada Buddhism as Thailand's dominant religion. It reached its height under the reign of King Ramkhamhaeng's grandson, king Li Thai (1347-1368 A.D.), when about 30 volumes of the Buddhist scriptures were studied and rewritten by the king into one volume, the Tribhumikatha, a treatise on Buddhist cosmology and the three planes of existence-Sensuous, Corporeal, and Incorporeal. Not only was this the first Buddhist treatise by a Thai, but it was this the first known Thai Buddhist literary work. The Tribhumikatha's impact on religious arts such as mural paintings can be seen today in many monasteries in various provinces.
Through the centuries Buddhism has been the main driving force in Thai cultural development. Much of classical Thai art, particularly architecture, sculpture, painting, and early literature, is really Buddhist art. Then and even now, Buddhism colors everyday Thai life.
Although Buddhism became the primary and state religion, Thais always subscribed to the ideal of religious freedom. Thai constitutions have stipulated that Thai king must be Buddhists, but monarchs are invariably entitles "Upholder of All Religions". Consequently, the government, through the Religious Affairs Department, annually allocates funds to finance religious education
and to construct, maintain, and restore monasteries, mosques, and churches.