The country has an area of 198,000 square miles (510,000 km2) and population of 70 million. According to the government's National Statistics Office, approximately 94.8 percent of the population is Buddhist and 4.5 percent is Muslim; however, non-governmental organizations, academics, and religious groups estimated that approximately 85 to 90 percent of the population is Theravada Buddhist and up to 10 percent of the population is Muslim . Christians, mainly Catholics, represent 0.7% of the population. There are small animist, Confucian, Hindu, Jewish, Sikh, and Taoist populations. According to the Ministry of Culture's Religious Affairs Department (RAD), the numbers of atheists or persons who do not profess a religious faith make up less than one percent of the population.
The dominant religion is Theravada Buddhism. The Buddhist clergy, or Sangha, consists of two main schools, which are governed by the same ecclesiastical hierarchy. Monks belonging to the older Mahanikaya school far outnumber those of the Dhammayuttika school, an order that grew out of a 19th-century reform movement led by King Mongkut (Rama IV).
Islam is the dominant religion in four of the five southernmost provinces, which border Malaysia. The majority of Muslims are ethnic Malay, but the Muslim population encompass groups of diverse ethnic and national origin, including descendants of immigrants from South Asia, China, Cambodia, and Indonesia. The RAD reported that there are 3,567 registered mosques in 64 provinces, of which 2,289 are located in the 5 southernmost provinces. According to the RAD, 99 percent of these mosques are associated with the Sunni branch of Islam. Shi'a mosques make up the remaining 1 percent.
According to RAD statistics, there are an estimated 351,987 Christians in the country , constituting 0.5 percent of the population. There are several Protestant denominations, and most belong to one of four umbrella organizations. The oldest of these groupings, the Church of Christ in Thailand, was formed in the mid-1930s. The largest is the Evangelical Fellowship of Thailand. Baptists and Seventh-day Adventists are recognized by authorities as separate Protestant denominations and are organized under similar umbrella groups.
According to the most recent government survey in 2002, there are 9 recognized tribal groups (chao khao), comprising approximately 920,000 personsSyncretistic practices drawn from Buddhism, Christianity, Taoism, and spirit worship are common among the tribal groups. The Sikh Council of Thailand estimates the Sikh community to have a population of approximately 70,000 persons, most of whom reside in Bangkok, Chiang Mai, Nakhon Ratchasima, Pattaya, Ko Samui, and Phuket. There are 18 Sikh temples in the country. According to RAD statistics and local Hindu organizations, there are an estimated 95,000 Hindus in the country.
The ethnic Chinese minority (Sino-Thai) has retained some popular religious traditions from China, including adherence to popular Taoist beliefs. Members of the Mien hill tribe follow a form of Taoism.
Mahayana Buddhism is practiced primarily by small groups of Chinese and Vietnamese immigrants. There are more than 675 Chinese and Vietnamese Mahayana Buddhist shrines and temples throughout the country.
Religious groups proselytize freely. Monks working as Buddhist missionaries (Dhammaduta) have been active since the end of World War II, particularly in border areas among the country's tribal populations. According to the National Buddhism Bureau, as of December 2006 there are 6,458 Dhammaduta working in the country. In addition, the government sponsored the international travel of another 1,414 Buddhist monks sent by their temples to disseminate religious information. Muslim organizations reported having small numbers of citizens working as missionaries in the country and abroad. Christian organizations reported much larger numbers of missionaries, both foreign and Thai, operating in the country.