Pre-Buddhist Thailand has had a significant hand in developing modern Thailand lore. Spirits have a minor place in Buddhist Thailand, but the phi is a collective term for spirits, similar to ghosts, goblins, elves, and fairies.
Many phi were malevolent and haunted homes and structures.
Among the phi who lived in the countryside included the ghosts of people who were killed by animals, women who died during childbirth, people who died and did not have proper funeral rites, and people who died suddenly. These were the sources of most vampire attacks, biting, scratching, and causing disease.
The Phi Song Nang was a spirit similar to the Pontianak of Java and Indonesia. The vampire spirit appeared as a young woman and attacked young men, vampirizing them.
In cases of a phi attack, a seer (or maw du) would be called. The maw du would use various spells and incantations to get rid of the phi. They would also use various charms to prevent an attack.