There once lived during the reign of King Mongkut (1851-1868) a beautiful girl named Nak, who was married to a man named Tid Mak. The love between Nak and Tid Mak bore fruit, and soon Nak was heavy with child. But as the Fates would have it, Tid Mak was called to serve in the Army, forcing him to leave his pregnant wife. While Tid Mak was away, Nak suffered a fatal complication while giving birth and died along with her child. But due to her deep love for her husband, Nak refused to cross over and instead remained as a ghost in their house.
When Tid Mak returned home, still blissfully unaware of his wife's death, he found his beautiful wife and child waiting for him. Not wanting his husband to know of her deathly situation, Nak killed anyone who attempted to warn her husband that he was living with a ghost. And for a time they lived a life full of happiness and love, plus the occasional brutal death of nosy neighbors.
But Nak could not have it her way for long, as fate again intervened to stop her murdering shenanigans. One day, as Nak was preparing lunch for her husband, she accidentally dropped a lime off the porch. She quickly reached out to catch the lime, but in her haste she overstretched her arm, elongating it to inhuman proportions (apparently, Thai ghosts are like Mr. Fantastic). Unbeknownst to Nak, Tid Mak saw the whole thing and at last realized that Nak was a ghost. Fear gripped Tid Mak, who did not wantto spend his life hitched to a ghost. He fled their house that night and took refuge inside a holy temple so that Nak could not chase after him.
When Nak realized that Tid Mak had fled, her grief knew no bounds. Grief quickly turned to anger and she went on a murdering rampage. Her neighbors got the brunt of her wrath, and dozens died by her hands. Wanting nothing more to do with her, the neighbors hired an exorcist to lock her up in an earthenware jar (Asian Ghostbusters-style) and toss the jar over the canal. For years afterwards, the village was at peace.
But the story does not end there - several years later, someone accidentally fished out the jar from the canal and unwittingly released the ghost of Nak. The one who vanquished her this time was the famous Buddhist monk Somdej Toh, who imprisoned her spirit in the bone of her forehead and bound it on his waistband. The priest from The Exorcist should really take a lesson from this guy.
When Somdej Toh died, the relic was said to have passed on to the Royal Family to make sure Nak would not be released to do harm ever again. Imagine that - she has the Royal Family as jail wardens.