Angkor's turn
Angkor's great temples were built for Śiva and Viṣṇu. Jayavarman VII, who ruled from about 1181 to 1218, made Mahāyāna Buddhism the religion of the court, built the Bayon, and founded hospitals dedicated to the healing Buddha. After his reign a Brahmanical reaction defaced many Buddhist images.
Theravāda arrived differently. It spread through the 13th and 14th centuries in Pāli, through village monks, probably by way of Mon and Thai networks, and seems to have taken hold from below rather than by royal decree. The Chinese envoy Zhou Daguan, who visited in 1296, describes monks in yellow robes with shaven heads, already a normal part of Khmer life.
Lan Xang
In Laos, Fa Ngum is credited in the 14th century with establishing Theravāda in the kingdom of Lan Xang, bringing with him the Phra Bang image from the Khmer court. Luang Prabang and later Vientiane became monastic centres, and Lao Buddhism settled alongside local phi spirit practice rather than replacing it.
The 20th century
French colonial rule reorganised Buddhist education and founded a Buddhist Institute in Phnom Penh, which produced the first printed Khmer canon. Then, under the Khmer Rouge from 1975 to 1979, the monastic order was dismantled: monasteries were emptied and used for other purposes, monks were defrocked, put to work or killed, and manuscripts were destroyed. Researchers estimate that only a small fraction of a monastic community numbering tens of thousands survived.
Both countries rebuilt. Cambodia restored its ordination lines with monks from abroad from 1979 onwards, and in Laos the order continues under a socialist state that for a time tried to redirect it.
Why it matters
It shows Buddhism reshaping, and being reshaped by, the traditions it met.
History and tradition
What historians can say
Angkor's inscriptions and archaeology, and Zhou Daguan's account, carry the early story. The figures for the Khmer Rouge years are estimates reconstructed afterwards from survivors and records, not counts, and they vary between researchers.