The monastic tradition in Thailand can be traced back to the time of King Asoka when, around B.E. 234 (310 B.C.), nine missions of monks were sent out as Dhamma messengers to propagate the Dhamma in different countries. One of the missions, headed by the Elders Soṇa and Uttara, came to Suvaṇṇabhūmi, which covered some parts of what we now call Thailand, and succeeded in establishing Buddhism there. We do not know much about the Buddhist situations and developments later than that time until the foundation of the present lineage of the Thai monastic Sangha in the Sukhothai period, around B.E. 1820 (1277 C.E.). We learn that at the time when the present form of monastic Sangha of the Laṅkāvaṁsa tradition was established in Sukhothai, there prevailed monks of some older local traditions. Before long, the monks of the older traditions became absorbed into the newly established Sangha.
The present tradition of Thai monastic Sangha was established under the full support of the King who himself invited the head monk from afar to found it and since then, throughout the different periods of over 700 years, it has enjoyed the status of the national Sangha under royal patronage and state protection. At present, the large Thai monastic community consists of about 400,000 monks and novices who are accommodated in more than 30,000 monasteries all over the country. In comparison with the whole Thai population of 48 million, of which about 93.4 percent are Buddhist, it makes Thailand deserve the name of the "Land of the Yellow Robe." The fact that such a large monastic community fares well under the support of a Buddhist population of that size shows clearly how devout and generous the Thai Buddhists are.
Right from the beginning, the Thai monastic Sangha has been divided into two sections, town-monks and forest-monks. The division is only a matter of specialization and there is a good relationship between the two, including the transfer of residents. Forest monks preserve the tradition of meditation, while town-monks specialize in study and engage in religio-cultural activities. In comparison with town monasteries, the number of forest monasteries is small.
The over 30,000 monasteries are also classified into two categories of royal monasteries and private or community ones. Royal monasteries are those erected by the King or having obtained his recognition. They are usually large and contain imposing edifices. Community monasteries are mostly smaller and simple. Only about 200 monasteries are royal and most of them are in the capital, while the majority are private or community ones scattered in the villages throughout the country.
The kings of Ayudhya, beginning 600 years ago, were much influenced by Brahminism and Brahmin advisers were consulted in cultural and administrative affairs. Consequently, Brahminical rites and ceremonies have continued in state activities side by side with the Buddhist ones. This has sometimes led to the mingling of the two. At the village level, the populace have been more or less attached to animistic beliefs and practices. Through the monks' association with these villagers, some animistic elements have crept into Buddhism. With the integration of animistic and Brahminical elements into Buddhism in the process of assimilation, there has developed a form of popular Buddhism, in which rites and ceremonies are predominant and superstitious beliefs and practices are prevalent.
Town and village monasteries have been, for Thais of all classes, centres of education, both religious and secular. There, basic subjects like reading, writing and arithmetic were taught to boys. The Thais have also developed a custom of temporary ordination. Every young man is expected to stay for a period of about three months (usually in the Vassa or the rainy season) in a monastery as a monk. Here it is education for socializing male members of the society, as they are expected to join the monkhood to undergo monastic and cultural training before running families and assuming other civic responsibilities, including civil and military services, as learned ex-monks. This custom has, however, been on the decline during the last half of the century.
Since the introduction of the modern Western system of education to the country about a century ago, Thailand has been experiencing the problem of inequality of opportunity in education, as large numbers of poor and underprivileged youngsters in the upcountry villages cannot get access to public and higher education. The monasteries have done much to help ease the situation as the monkhood has been the channel of education for these sons of the peasants and villagers from distant areas. Thus, the monastic systems of education in present-day Thailand, whether the traditional system of Pali and Dhamma studies, or the two Buddhist universities in Bangkok, together with their affiliated colleges in the provinces, not only provide monastic learning for monks and novices, but also serve the educational needs of the Thai society as a whole.
Monasteries have been seats of Thai culture and Buddhism has been a foundation of the Thai culture. Arts and architecture have been developed and preserved in the monasteries. A large number of Thai words, especially almost all technical terms, are derived from Pali and Sanskrit. Thai literature has been based to a large extent on Buddhist literature. In fact, most of the Thai literary works in the past were Buddhist in nature and were written by monks in the monasteries. Besides, the monasteries have been centres of social activities, where people assemble in large gatherings, both on religious and on civic occasions, including temple fairs.
Although, since the arising of the Dhammayut group (also called Dhammayuttikā) about one and a half centuries ago, the Thai monastic Sangha has been divided into two denominations or suborders of the Mahānikāya and the Dhammayut, the whole monastic community is still unified under one and the same governing body, called the Council of Elders, or the Sangha Supreme Council, presided over by the Supreme Patriarch. The State has enacted laws forming a Constitution under which the monastic Sangha governs itself. According to the present act of B.E. 2505 (1962 C.E.), the Sangha administration is based on the process of centralisation. The Supreme Patriarch, who is appointed by the King, has absolute power to govern the whole monastic community and to direct all ecclesiastical affairs. Under him is the Sangha Supreme Council, which serves him as the Consultative Council. Under this highest governing body, at the local administrative level, 73 ecclesiastical provincial governors are responsible for provincial affairs of the Sangha, each in his respective province.