Khmer Religion. Since the ancient time,
the Khmers had accepted the two great religions from India, i.e.
Hinduism and Buddhism, by which the former one was more popular.
Hinduism had played an important role in Khmer civilization as the
Angkor monarchs adopted its concept of deva-raja, or “god-king”, by
which the king was revered as an incarnation of the god Shiva, a
supreme Hindu deity who was regarded as a protector.

Most temples in the Angkor Empire were dedicated to either god Shiva or
god Vishnu. Believed to be the holy house of the supreme gods, the
temples were carefully built with fine arts, and the materials used are
those of everlasting stones. Many impressive sculptures of great
craftsmanship were enshrined.
The second religion being revered by the Khmers was Buddhism of
Mahayana sect which came into the region quite at same time as Hinduism,
however, Buddhism was less prominent.
Both Hinduism and Mahayana Buddhism played an important role as the
political, religious and philosophical pillars of Khmer Civilization by
which the king was revered as the god-king or deva-raja. This ideology
enabled the king to rule over the country as an absolute monarch with
sovereign spirituality over his people, and thus enhanced the unity of
the kingdom. Successive kings were able to mobilize large manpower to
serve the army, to maintain extensive irrigation system and to build
numerous massive temples.
Not until the 13th century, Theravada Buddhism was introduced to the
Khmer from Sri Lanka and became more prominent in the royal court as
well as in the local people. The teaching of Theravada Buddhism
directly crashed with the original belief of the Khmer people as it
taught the people to seek self enlightenment and abandoned the worldly
things. With this teaching, the attitudes of the people towards its
Hindu gods as well as the god-king changed, and thus led to the gradual
weakening of the empire which eventually collapsed in the first half of
15th century.
The Khmer people seem to be the obedient students, as they did not
raise doubts about the riligious teaching of the original doctrines. We
can see in Khmer history that the religions such as Hinduism and
Buddhism were not divided into the different sub-sects in the land of
Khmer, as they were so in some other civilizations.
In addition to Hinduism and Buddhism, the Khmer people also had their
own indigenous beliefs such as the local deities, ancestral spirits, as
well as the evil spirits. There are no inscriptions or manuscripts to
describe these beliefs, however, it can be found to be prevalent in
modern Cambodia, especially in the remote villages. These beliefs are
passed on from one generation to another through the words of mouth.