Tantric Theravada, Esoteric Southern Buddhism and Borān kammaṭṭhāna ('ancient practices') are terms used to refer to certain Tantric and esoteric practices, views and texts within Theravada Buddhism. L.S. Cousins defines this tradition as "a type of Southern Buddhism which links magical and, ritual practices to a theoretical systematisation of the Buddhist path itself", though he feels the term Tantric is a too specific term to be used. One specific kind of Tantric Theravada is termed the Yogāvacara tradition and this kind of esoteric Buddhism is most widely practiced today in Cambodia and Laos and in the pre-modern era was a major Buddhist current in Southeast Asia. In the west, the study of Tantric Theravada was pioneered by professor François Bizot and his colleagues at the École française d'Extrême-Orient with a particular focus on the material found at Angkor.
Historically, the Buddhists of Abhayagiri vihāra in Sri Lanka are known to have practiced Tantric Vajrayana and Mahayana and this might have had an influence on Southeast Asia through their missionary work in Java. Ari Buddhism was a form of Buddhism practiced in the Mon kingdoms of Burma which also contained Tantric elements borrowed from India and local Nat (spirit) and Nāga worship. In many of Bizot's works there is some suggestion that the Buddhism of the Mon may have influenced the later Yogāvacara tradition. It is also possible that Southeast Asian Buddhism was influenced by the practice of Hinduism and Mahayana Buddhism which flourished in Southeast Asia during the time of the Khmer Empire. According to Lance Cousins, it is also possible that 'Tantric Theravada' developed within the "orthodox" Mahavihara tradition of Sri Lanka, citing the 5th century Buddhist scholar Buddhaghosa's mention of secret texts (gulhagantham) as well as other textual evidence from the Pali commentaries. Cousins concludes that "It is quite possible that present-day esoteric Buddhism contains ideas and practices deriving from more than one of these sources. Nevertheless it is certainly premature to assume that it has its origins in unorthodox circles."
The Tantric Buddhist Yogāvacara tradition was a mainstream Buddhist tradition in Cambodia, Laos and Thailand well into the modern era. An inscription from Northern Thailand with tantric elements has been dated to the Sukhothai Kingdom of the 16th century. Kate Crosby notes that this attestation makes the tantric tradition earlier than “any other living meditation tradition in the contemporary Theravada world.”
During the reign of Rama I, the Thai Yogāvacara master Kai Thuean (1733-1823) was invited to Bangkok to be head of the meditation tradition there and was later made Sangharaja (head of the religious community) by Rama II of Siam in 1820. In Sri Lanka, a revival of Buddhist meditation in the 1750s saw a proliferation of Yogāvacara teachings and texts by Thai monks from the Ayutthaya Kingdom, one of which is the Yogāvacara's manual. Monks of the Siam Nikaya practiced these teachings and established several monasteries around Kandy. As late as the 1970s, Yogāvacara practices such as the rapid repetition of Araham were recorded in Sri Lanka.
The decline of the Tantric currents in Theravada Buddhism began with the rise of the reformed Buddhist modernism in the 19th century, particularly the Dhammayuttika Nikaya established by King Rama IV (1851–1868) of the Thai Rattanakosin Kingdom in 1833, which was imported into Cambodia as it was a protectorate of the kingdom. In establishing the Dhammayuttika Nikaya, Rama IV emphasized the use of the Pali Canon as the main authority for monastic practices and also attempted to remove all superstitious and folk religious elements. The textual tradition followed by this reform movement was that of the Sri Lankan Mahavihara school (which itself dates from a set of 12th century reforms) which took the works of the 5th century scholar Buddhagosa as representing the orthodox interpretation and thus saw other Buddhist practices as unorthodox. The reforms tightened monastic discipline and led to a decline in the practices and production of texts which were not in line with Dhammayuttika Nikaya orthodoxy. When Cambodia came under the rule of the French colonial empire, the French continued this policy of suppressing pre-reform Cambodian Buddhism. In spite of this, traditional Tantric practices survived in rural areas.
The devastation of Cambodian religion by the Khmer Rouge and religious repression in Communist Laos also had a heavy toll on these traditions. Tantric Buddhist influences may be present in the practices and views of the modern Thai Dhammakaya movement as well as in certain South Asian religious practices such as the use of protective tattoos and amulets, the singing of protective Gathas (e.g. Jinapañjara Gāthā), Thai astrology and the invocation of spirits and ghosts (such as Somdej Toh and Mae Nak). Today, tantric magicians and tantric forest monks are most prevalent in the banks of the Mekong in Cambodia and Laos and are believed to have magical powers, the divine eye and the ability to communicate with spirits. They practice Kasina meditation, mantra recitation, and ascetic practices (dhutanga). Thai forest monks such as Ajahn Lee Dhammadharo were also influenced by the tantric practices as is exemplified by his text "The Divine Mantra."
L.S. Cousins sees the practice of Tantric Theravada as being defined by the mapping of inner and outer worlds, and calls it 'tantro-kabbalistic' mysticism. By this he means "a form of mysticism which utilizes a rather elaborate map of correspondences -between the human body, the cosmos and some kind of higher reality or knowledge. In the process it draws on the full resources of the widely-dispersed traditions of magic and the occult - letter, sound and number symbolism together with the use of structured patterns of shape or gesture."
Two of the most widely used sacred mantras in Yogāvacara texts are Namo Buddhaya ("Homage to the Buddha") and Araham ("Worthy One"). Here is an example of esoteric interpretation of the letter and number symbolism of Namo Buddhaya:
The recitation of these sacred phrases was used as a meditation practice. Robert Percival (in Ceylon from 1796 to 1800), described Buddhist mantra meditation thus: "To their girdles they wear suspended strings of beads made of a brownish or black wood; and mutter prayers as they go along."
In one text studied by Bizot, meditation includes the use of visualization of colored lights paired with sacred syllables located throughout the body and visions of the Buddha and a stupa at the top of mount Sumeru. Another text called the Ratanamala uses the itipi so formula for various purposes including spiritual protection, magical 'worldly' uses which are termed "left-hand", the transformation of the body into a kayasiddhi, a spiritual body, as well as for the pursuit of nirvana (termed "right-hand path").
Several studies by Bizot have also looked at certain "rebirthing" rituals which seem to have been common in pre-modern Cambodia. They included symbolic sacred syllables, the entrance into a cave which symbolized the womb, meditation on embryonic development, and the belief that this meditation would allow one's body to be reborn as the Dharmakaya. Another practice studied by Bizot was the use of yantras or sacred diagrams, which were made with Pali words and phrases and used as tattoos and on clothing.
In his study of the Saddavimala, a Yogāvacara text which was widely circulated in Southeast Asia (with over two hundred extant manuscripts), Bizot gives an outline of Yogāvacara practice:
In contemporary Southern Buddhism, these practices are sometimes termed Boran Kammatthana (ancient practices) and are most widely seen in Cambodian Buddhism. They usually involve "the physical internalisation or manifestation of aspects of the Theravada path by incorporating them at points in the body between the nostril and navel."
The practices of the Burmese Buddhist Weizza ("Wizards") who follow an esoteric system of occult practices (such as recitation of spells, samatha and alchemy) which are believed to lead to supernormal powers and a life of immortality might also be related to the pre-modern tantric and mystical practices.