The krasue, known as Ap in Cambodia and as Kasu in Laos, is a nocturnal female spirit of Southeast Asian folklore. It manifests itself as a woman, usually young and beautiful, with her viscera hanging down from the neck, trailing below the head.

According to Thai ethnographer Phraya Anuman Rajadhon the Krasue consists of a floating head accompanied by a will-o'-the-wisp kind of glow. The explanations attempted about the origin of the glow include the presence of methane in marshy areas. The Krasue is often said to live in the same areas as Krahang, a male spirit of the Thai folklore.

This spirit moves about by hovering in the air above the ground, for it has no lower body. The throat may be represented in different ways, either as only the trachea or with the whole neck. The organs below the head usually include the heart and the stomach with a length of intestine, the intestinal tract emphasizing the ghost's voracious nature. In recent movie Krasue Valentine, this ghost is represented with more internal organs, such as lungs and liver, but much reduced in size and anatomically out of proportion with the head. The viscera are sometimes represented freshly daubed with blood, as well as glowing. In contemporary representations her teeth often include pointed fangs in yaksha or vampire fashion.In the movie Ghosts of Guts Eater she has a halo around her head.

http://theunexplainedmysteries.com/Krasue-Floating-Head-Ghost.html