Little is known about the earliest form of Buddhism in the Mon country, although it is likely to have been similar to that present among the Pyu.  In more recent times the form of Buddhism present among the Mon has often been a rather conservative type of Southern Buddhism, emphasizing the purity of its monastic lineage and practices.  At a popular level, village practices of great antiquity continue.

A tradition current in Ceylon by about the third century A.D. claims that missions were sent in the third century B.C.  by the Indian Emperor Asoka to Goldenland (Suvannabhumi).  This would probably have been somewhere in the lands (later?) dominated by the Mon (southern Burma, central and northern Thailand), but there is no historical evidence to confirm or refute that claim.  It is certain that in the last centuries B.C. there was trade between Southern India (including Ceylon) and South-East Asia and a South Indian alphabet was adopted around this time.  We may be certain that Ceylon-style Buddhism was introduced throughout this area, if it was not already present.  It probably remained the dominant Buddhist tradition thereafter, despite the presence of various other forms of Buddhism and Hinduism in the other.
    The precise history during the first millennium A.D. of the Mon kingdoms of Ramanna (Pegu) in lower Burma and Dvaravati, later Lamphun and Lopburi, in Thailand is unknown.  It is likely, however, that all were strongholds of Southern Buddhism (and perhaps other forms of Buddhism too).  In any case the orthodoxy of the Buddhism in Ramanna was sufficiently unquestioned for the eleventh century Sinhalese king Vijayabahu to restore the ordination lineage of the three monastic fraternities from there.  During much of the second millennium too, the Mon kingom of Ramanna (sometimes under Burmese rule and sometimes a more or less independent state) was a major conduit for influences and innovations coming from Ceylon and spreading out across South-East Asia.

Those of ancient Buddhism: the twelve- or eight-spoked wheel, the bodhi tree, the throne, the footprints of the Buddha, the stupa and later the Buddha image.

Mon speakers still number about a million and a quarter, mostly in Burma but some in Thailand.  (It is likely that many Thais and Burmese are of partly Mon descent.)  They preserve some traditions of their own, but have been heavily influenced by more recent developments in the Buddhism of the Burmese and the Thais.

Thaton, Pegu