See Uey Sae Ung, aka Si Oui, was a Chinese immigrant who moved to Thailand in 1944. He was a former soldier, fighting against the Japanese during World War II. Some people claim that his lust for human flesh started on the battlefields, as commanders told the troops to eat the livers of enemy soldiers to take on their strength and power.
Many civilizations throughout time thought that the liver was the center of life of the body and was praised for its regenerative properties. Therefore it is believed that eating the livers of enemies would not only dehumanize them, but also enable the soldiers to absorb their strength.
Si Oui is believed to have raped, and suffocated 5 to 8 male children in the vicinity of Bangkok during the 1950's. He then ate their hearts and livers. His goal was to become stronger, healthier, even immortal.
He was caught in the act by a young boy's father as he was burning one of the bodies, and executed.
After his autopsy, his corpse was preserved and can still be seen today in the Songkran Niyomsane Museum of Forensic Medicine in Bangkok. Over the years, he has become the Thai Bogeyman, parents scaring their children by telling them that if they don't behave, his ghost would come and hunt them.