In the late 19th century French archaeologists at Angkor discovered a statue of a squatting, bare-chested man, his right hand apparently once holding a rod or similar object, on a terrace next to the Bayon temple. Presumably it had been there for centuries, as the terrace was used in ancient times for royal cremations and perhaps for judgements. The statue, according to its inscription, was Yama, the god of death and judgement, but the local villagers were worshipping it as Sdach Kamlong, the Leper King, who, as legend has it, was Preah Thong, the Indian prince who married the naga princess and was first to rule over the Khmer people.
Preah Thong was warned by his wife’s father, the naga king, not to build a four-faced tower in his city, but he ignored the warning. Using the magical power of the four faces he captured the naga king and imprisoned him inside the tower, but the serpent escaped and sought to kill him. Each dealt the other many grievous wounds, but Preah Thong eventually dealt the fatal blow, although he was stained by the naga’s venom. The dying naga warned him not to remove the poison, but Preah Thong washed his body, and so was stricken with leprosy as a visible sign of his deed.
Seeking to cover up the murder from the naga’s daughter, Preah Thong killed a monk, thinking he could be reincarnated in the monk’s healthy body. This was a crime even worse than killing his father-in-law, and his outraged courtiers banished him to the forest, while his city became the haunt of monkeys and tigers. Eventually, after many trials, he was cured by the power of the sacred waters of the Ganges (the Siem Reap River) and restored to his city and throne.
The legend of the Leper King and the abandoned city is an allegory of the fall of Angkor and a hope for national salvation. However, the story is certainly older than the fall of Angkor, for the medieval Chinese traveller, Zhou Daguan mentions that a king of Angkor once fell victim to leprosy.
The statue is now in the central courtyard of the National Museum in Phnom Penh, where worshippers ask for health and prosperity and for protection from danger. It’s especially popular with students from the University of Fine Arts next to the museum, and special ceremonies with offerings of flowers and fruits and music are held at New Year and Pchum Ben (the festival of the dead).
According to popular belief the Leper King was Yasovarman I. This cannot be true, for the following reasons: (1) There is nothing to indicate that the statue represents a king or a leper or even that the terrace was its original home; (2) there is no evidence that Yasovarman or any other Khmer king was a leper; and (3), Yasovarman’s capital was somewhere else and the terrace wasn’t built till long after his death. (The acerbic note comes from my source, a rather mysterious but apparently well-informed pdf file by someone who goes by the single name of Sokheoun. Sokheoun is a stickler for facts, one of which is fascinating: it seems that, deep inside the Bayon temple at Angkor, there’s a series of bas-reliefs illustrating the Leper King story).
The myth of the Leper King is very much alive and well. Here’s some Cambodians discussing it on khmerconnection in 2009. The version of the legend someone gives here is slightly different from ine, but that’s how it goes with legends. Note the way they join the dots between the legend and modern politics: