As a general introduction to the naga (pronounce: naaga) one might repeat Suhas Chatterjee’s “Indian Civilization and Culture” (Delhi 1998):
“The Naga or serpent cult had been a dominant cult all over India. The two seals of Indus valley demonstrate the serpent worship prevalent among the Mohenjodaro people. In (the vedic scriptures) Yayur Veda and Atharva Veda we get the reference of serpent worship. During the reign of Kushana king Hubiska (ruled between 111 and 180 [and must have ascended the throne as an infant]) a naga statue was installed in a tank (a water reservoir). The naga was considered the guardian of the treasures and the guiding spirit of the departed soul of the ancestors. … (Hindu god) Vishnu rests on the S(h)esa naaga, (hindu god) S(h)iva wears snake (phanibhusan). Parsvanath, the Jaïn saint has the snake symbol.”
Mr. Chatterjee’s entry says nothing about a nine-headed naga, but India Profile states that in Hindu philosophy the snake with “nine heads represents finality, unity with the forces of nature and the ideal state of spiritual liberation.”
There are some more references to nine-headed nagas in Hindu literature, but they all seem to amount to the same concepts of finality, auspiciousness, and even are seen as an avatar of god Vishnu.
One might think that the nine-headed naga is a Khmer-adaptation of the Indian Hindu lore, but Zhou Daguan, a Chinese envoy in the late 13th century, relates a legend regarding the Phimeanakas, one of the Cambodian Angkor-monuments. He says:
“Inside the palace there is a gold tower [the Phimeanakas], at the summit of which the king sleeps at night. The local people all say that in the tower lives a nine-headed snake spirit which is the lord of the earth for the entire country. Every night it appears in the form of a woman, and the king first shares his bed with her and has sex with her. […] If for a single night this spirit does not appear, the time has come for this […] king to die. If for a single night he stays away, he is bound to suffer a disaster.” (http://www.angkorguide.net/en/library/naga/naga693.html)
It is of interest to note that the Mekong river was of old called the river of nine dragons. Naga, dragon, nine, all these have been powerful symbols in Indo-China, in India, and in China.
Indo-China developed its own mythology concerning the snake that in a deïfied form appeared as naga, even a naga with multiple heads, upto nine heads.
Did the Khmer kings, or rather, did their purohita (Hindu or Brahmanical house priest) adjust the indigenous legends around the snake/naga to fit or co-embrace the Indian symbol, and was the Indian lore their only reference, or the reference that building masters-cum-artists relied on?
As we see above Chinese envoys were sent to the Angkor court, and Angkorians most certainly have travelled to China. And China too had its mythological theories about snakes and a nine-headed snake monster by the name of Xiangliu. And Chinese mythology knows Kung Kung, the serpent god with nine heads, a god of wisdom.
Furthermore, says another source, “The number nine is special in China as it is the largest possible single digit. … Nine was considered the number of the emperor.”
Hence we might conclude that the Khmer kings and their courtiers did not only amalgamate Hinduïsm, Buddhism (that knows a naga in its one-, respectively five-headed form) and the indigenous belief system, but at least it tried to please the Chinese envoys as well. By positioning nine-headed nagas at the entrance of their palatial complexes they sent the message abroad: the Chinese emperor, might he wish to visit us will be welcomed by the number nine that he alone is allowed to employ, either in artefacts or in embroideries on his costumes. And at the same time the Khmer king issued an implicit statement: me too, I’m an emperor in my own right.