For decades, some parents in Thailand warned their naughty children that if they did not behave, Si Quey would come eat their livers.If the threat of a ghostly visit from the executed child killer, long called a cannibal, proved ineffective, those children could always be taken to see Si Quey. His mummified corpse – gnarled and blackened – for years stood on display in a glass case in the Forensic Museum at Bangkok’s Siriraj Hospital.In recent years, however, doubts were raised about whether…