Theravada Buddhism is the state religion of Cambodia, which has been present since at least the 5th century.
Suvannaphum King Ashoka sent missionaries to the land of Suwannaphum, which has sometimes been identified as the mainland southeast Asian region of Mon (now a state in Myanmar, the state of Mon) and Khmer (now Cambodia) people. The Mahavamsa, a Sinhalese Pali chronicle, mentions these missions.The Mahavamsa, chapter 12, translated by Wilhelm Geiger
"Unconfirmed Singhalese sources state that Buddhism was introduced to Suvannaphum, or the 'Golden Peninsula', as mainland Southeast Asia was once referred to, in the 3rd century B.C. under the reign of King Ashoka, the great Buddhist ruler. According to these sources, two monks, Sona and Uttara, were sent to propagate the doctrine of the Master in this region following the great council of 274 B.C. held in Asoka's capital Pataliputta, India. While this mission may be legendary, it indicates that Buddhism has been present in Southeast Asia for a long time. Various Buddhist sects and schools, including Tantrism, vied or coexisted with a dominant Brahmanism and indigenous animistic faiths for centuries before the rise of the classical Southeast Asian empires beginning in the 9th century A.D. In part through Indian merchant traders, Indian cultural influence was pervasive in this early period. In Funan (1st to 5th century A.D.) the first organized Khmer polity, the Khmer people embraced not only the diverse Brahmanic and Buddhist religions but also the social customs and mores of India."Tully, John. France on the Mekong.
Funan Kingdom In the period between 100 BCE and 500 CE, the Kingdom of Funan in the present-day Mekong Delta established a flourishing seafaring trade between China, Indonesia, and India. This kingdom was Hindu, with the kings of Funan sponsoring the worship of Vishnu and Shiva. Buddhism was already present in Funan as a secondary religion in these earliest times.
A Sanskrit inscription from 375 documents the presence of Buddhism in Funan. King Kuandinya Jayavarman (478-514) cultivated Buddhism and sent a Buddhist mission complete with Funanese Buddhist images, carved in coral, to the Emperor of China.Gyallay-Pap, Peter. "Notes of the Rebirth of Khmer Buddhism," Radical Conservativism.
Another early inscription in Sanskrit dated 586–664 at Wat Prey Vier notes that two Buddhist monks named Ratnabhanu and Ratnasimha were brothers. Chinese texts attest that Buddhism flourished in Cambodia in the last half of the 5th century, and that King Jayavarman sent the Indian monk Nagasena to present a memorial in the Chinese Imperial court.Dawson, Philip. The Art of Southeast Asia.
Buddhism was clearly beginning to assert its presence from about year 450 onward, and was observed by the Chinese traveler I Ching toward the close of the seventh century.
Chenla Kingdom The Kingdom of Chenla replaced Funan and endured from 500 to 700. Chenla extended from the Mekong Delta, and along the lands surrounding the Mekong and Tonle Sap rivers.
"According to Ma Touan-Lin, a 13th century Chinese chronicler, there were ten monasteries of Buddhist monks and nuns studying the sacred texts in the 4th and 5th centuries. He stated that two monks from Funan traveled to China in this period at the request of the Chinese emperor, to translate the Sanskrit Tipitika into Chinese. A passage from the History of Leang, a Chinese chronicle written in 502-556, tells us that King Rudravarman sent a mission of monks to China in 535 under the direction of an Indian monk, Gunaratana. The delegation arrived in China in 546, accompanied by 240 palm leaf manuscripts of Mahayana Buddhist texts. Evidence of a cult of Buddha's relics was seen in Rudravarman's request of the Chinese emperor for a long relic of Buddha's hair."Ray, Nihar-Ranjan. Sanskrit Buddhism in Burma.
Buddhism was weakened in the Chenla period, but survived, as seen in the inscriptions of Sambor Prei Kuk (626) and those of Siem Reap dealing with the erection of statues of Avalokitesvara (791). Some pre-Angkorean statuary in the Mekong Delta region indicate the existence of Sanskrit-based Sarvastivada Buddhism.
Khmer-style Buddha images are abundant from the period of 600–800. Many Mahayana bodhisattva images also date from this period, often found alongside the predominantly Hindu images of Shiva and Vishnu.
An inscription from Ta Prohm temple in Bali province, dated about 625, states, that the Buddha, Dharma and Sangha are flourishing.
Angkor Kingdom The transition from Hindu god-king to Mahayana Buddha-king was probably gradual and imperceptible. The prevailing Vaishnavite and Shaivite faith traditions gave way to the worship of the Gautama Buddha and the Bodhisattva Avalokitesvara.
King Jayavarman II (802-869) is the first real Khmer king of the Angkor Empire. He proclaimed himself god-king and began to establish the capital of Angkor (Rolous) near present-day Angkor Wat.
The Buddhist Sailendra kingdom exercised suzerainty over Cambodia as a vassal state during the end of the eighth and the beginning of the ninth centuries. As a result, Jayavarman, as a young man, had lived in the court of Java and had visited Sumatra. When he returned to Cambodia, he proclaimed himself a god-king (deva-raja) according to Khmer traditions, identifying himself with Shiva. Nevertheless, he was increasingly friendly to and supportive of Mahayana Buddhist influence throughout his kingdom.O'Murray, Stephen. Angkor Life.
When King Jayavarman II returned to Cambodia from Java, he built three capitals in succession: Hariharalaya, Amarendrapura, and Mahendraparvata. One of these, Amarendrapura, identified with Banteai Chmar, was a Mahayana Buddhist city presided over by Avalokitesvara, the Buddhist bodhisattva of compassion.
Mahayana Buddhism therefore became increasingly established in his empire. The form of Mahayana Buddhism that was propagated in the Srivijaya lands was similar to the Pala Dynasty Buddhism of Bengal, and of the Nalanda University in northern India.
"The Bengal University of Nalanda in Megadha (now Behar) was the theological center of Mahayana Buddhism under the protection of the Pala Dynasty [750-1060]. Shivaist interpretations of Buddhism, tinged with Tantric mysticism (that may have revived portions of pre-Aryan northeastern Indian faith traditions) were worked out in Megadha and then were exported throughout insular and peninsular Southeast Asia, particularly to Java. Yashovarman I (889-910), who ruled from the vicinity of Rolous in the late ninth century, seems to have been a Shivite Buddhist influenced by Nalanda syncretism. His successors (notably Jayavarman IV) dedicated themselves to Vishnu and Brahma, as well as to Shiva, with whom they continued to be identified by hereditary families of priests. Rajendravarman II studied Buddhism intensely."
The Sailendra dynasty also built the fantastic Mahayana Buddhist temple Borobudur (750-850) in Java. Borobudur appears to have been the inspiration for the later fabulous Angkor building projects in Cambodia, particularly Angkor Wat and Angkor Thom.
The primary form of Buddhism practiced in Cambodia during Angkor times was Mahayana Buddhism, strongly influenced with Tantric tendencies.
"The prevalence of Tantrayana in Java, Sumatra and Kamboja [Cambodia], a fact now definitely established by modern researches into the character of Mahayana Buddhism and Sivaism in these parts of the Indian Orient. Already in Kamboja inscription of the 9th century there is definite evidence of the teaching of Tantric texts at the court of Jayavarman II. In a Kamboja record of the 11th century there is a reference to the 'Tantras of the Paramis'; and images of Hevajra, definitely a tantric divinity, have been recovered from amidst the ruins of Angkor Thom. A number of Kamboja inscriptions refer to several kings who were initiated into the Great Secret (Vrah Guhya) by their Brahmanical gurus; the Saiva records make obvious records to Tantric doctrines that had crept into Sivaism."
"But it was in Java and Sumatra that Tantrayana seems to have attained greater importance. There Mahayana Buddhism and Shaivism, both deeply imbued with tantric influences, are to be seen often blending with one another during this period. The Sang Hyang Kamahayanikan, consisting of Sanskrit verses explained by an Old Javanese commentary, professed to teach the Mahayana and Mantrayana."
The presence and growing influence of Buddhism continued as the Angkor empire increased in power. King Yosavarman built many Buddhist temples in 887–889, representing the mandala of Mount Meru, the mythical axis of the world. The largest of these temples is Phnom Kandal or "Central Mountain" which lies near the heart of the Angkor complex.
King Rajendravarman II (944-968) "studied Buddhism intensely. Although he decided to remain a Shivaist, he appointed a Buddhist, Kavindrarimathana, chief minister. Kavindrarimathana built shrines to Buddha and Shiva. Jayavarman V (son of Rajendravarman) also remained a devote of Shiva. He, too, permitted his own chief minister, Kirtipandita, to foster Mahayana Buddhist learning and divination."
Suryavarman I Suryavarman I (1006–1050) is considered the greatest of the Buddhist kings, with the exception of Jayavarman VII.
The origins of Suryavarman I are unclear but evidence point that he began his career in northeastern Cambodia. He came to the throne after a period of disputes between rival claims to the Khmer throne. However, the term "usurper" is not appropriate when speaking in the Khmer context of royal succession as the Khmer throne did not exclusively include paternal lines but also recognized and even valued more to an extent the royal maternal line.
A strong proponent of Mahayana Buddhism, he did not interfere or obstruct the growing presence and dissemination of Theravada Buddhism during his reign.
Jayavarman VII Jayavarman VII (1181–1215) was the greatest of all Khmer Buddhist kings. Jayavarman VII worked tirelessly to establish Buddhism as the state religion of Angkor.
He was already an elderly man, perhaps 60, when he ascended the throne. Before becoming king, he had devoted his long life to meditation and tantra.
Sensing his mortality he worked feverishly to accomplish his works in "saving" the Khmer people and establishing a Buddhist empire in a race against time.
In 1177, the Cham Kingdom of central Vietnam had invaded and sacked Angkor, creating a sense of trauma and crisis throughout the Khmer Empire by attacking and looting the capital. King Jayavarman VII ascended the throne in a climate of crisis, and war.
Jayavarman VII was a Mahayana Buddhist, and he regarded himself to be a Dharma-king, a bodhisattva, whose duty was to "save the people" through service and merit-making, liberating himself in the process.
Scholars speculate why Khmer royalty rejected Hinduism and embraced Buddhism definitively at this time. Perhaps, they suggest, Jayavarman and his people had become disillusioned with the Hindu gods because of their failure to protect the Angkor Empire from being sacked by their enemies, the Cham. The Cham themselves were Hindu and worshiped Shiva, and the Khmer may have therefore felt an instinctive revulsion at the religion of their enemies.
Jayavarman withdrew his devotion from the old gods and began to identify more openly with Buddhist traditions. His regime marked a clear dividing line with the old Hindu past.
Before 1200, art in the temples mostly portrayed scenes from the Hindu pantheon such as Vishnu reclining on a lotus leaf, or the churning of the primeval sea of the milk of creation. After 1200, scenes from the Buddhist Jatakas, and life of the Buddha, along with scenes of the Ramayana began to appear as standard motif.