Fearsome ghosts in Thai belief. They can possess a human being and feed on the intestines. They can be expelled by a spirit doctor or exorcist (mhor phi) who performs a "whirlpool dance." The ghost, watching the dance, is sucked into the whirlpool and is thus removed from the body.
The legend of this ghost originated with a prince who found a magical way to enter the body of another living person or animal. When he performed this feat and entered the body of an animal, his servant, who had been listening to the magic words, repeated the incantation and entered the body of the prince. The prince, unable to return to his own body, transferred to that of a bird and flew to his wife to tell her what had happened. She immediately had the servant's body destroyed and challenged the false prince to enter the body of an animal. When he did, the real prince quickly re-entered his own body. The servant, unable to return to his body, is since then forced to going from one body to the next, eating the intestines.
Phi pop is also said to be a female ogre who feeds on human intestines and/or the blood of animals at night.