The story of Mae Nak Phra Khanong (or simply Mae Nak) is a well known and popular Thai ghost story.
The story, as told, happened during the reign of King Mongkut. The story concerns the beautiful Mae Nak (literally "Mother Nak"), a native of Phra Khanong in Bangkok, and her husband, Mak.
With Nak pregnant, Mak is called off to war (in some versions of the story the war is against the Shan tribe, while others are not specific), and is severely injured. While he is being nursed in central Bangkok, both Nak and the child she is carrying die during childbirth. When Mak eventually returns home, however, he is cast under a spell and finds his loving wife and his new child waiting for him and nothing wrong. Neighbors, who try to tell Mak of the death of his wife and to warn him that he is living with her ghost, meet with grisly ends.
One day, while Nak is preparing nam phrik, she drops a lemon down to the cellar. In her haste, the ghost extends her arm to pick the lemon from the upper floor through the floor's hole, not knowing that Mak saw the whole event. Terrified, Mak realises she is a a ghost, and connives to flee. At night, Mak lies to Nak and says that he wants to leave their the hut to urinate. He then breaks a little hole in an earthen jar which is filled with water, so that Nak will think that he is urinating, and Mak flees.
After discovering her husband's leaving, Nak pursues him. Mak sees his wife's ghost and conceals himself in a Blumea bush. (It is traditionally believed that ghosts are afraid of Blumea). Mak then runs to the temple of Wat Mahabut, where Nak cannot enter the shrine. Nak subsequently terrorizes the people of Phra Khanong as she expresses her anger with them for helping Mak to leave her.
Eventually, Nak's ghost is exorcised by a powerful exorcist, who confines her within an earthen pot which is thrown into the river.
There are several versions of the story at this point. In one, an old couple, new residents to Phra Khanong, acquire the ghost pot while fishing, while in another it is two fisherman (age and residency unknown) who dredge up the bottle. Nak is then freed by the unwitting couple, or the fisherman (depending on which version you read).
Eventually, Nak is suppressed by the venerable monk, Somdet Phra Phutthachan, and again there are several versions of the story. In one, the monk confines her within the bone of her corpse's forehead, and binds that bone within his waistband (and, according to a legend, the waistband passes through the hands of various persons and is currently in the possession of royalty). In another, the monk foretells that in a future life Nak will be reunited with her husband, and so the ghost voluntarily leaves for her next life.
Mae Nak's story is popular because of her true love and devotion for Mak.
Though there is no evidence that the legend is true, there is a shrine dedicated to Mae Nak at Wat Mahabut (which was situated in the Phra Khanong district until a 1997 boundary change placed it in neighboring Suan Luang district - much to the consternation of the people of Phra Khanong).
The Shrine of Mae Nak
The shrine of Mae Nak can be found at Wat Mahabut, which is down a small soi (side road) off Sukhumvit soi 77, also known as Onnut Road (sometimes spelled "Onnuj" or "On Nut"). Probably the easiest way to get there is to take the Sukhumvit line of the BTS Sky Train all the way to its terminal station at Onnut, then backtrack a short way until you reach Onnut Road (Sukhumvit 77) on the north side of the road. About 1km down Onnut road, on the left, you will find a small lane signposted as soi 7. Wat Mahabut and the Mae Nak shrine are to be found at the end of the lane, with the shrine at the far side of the compound near the canal known as Klong Phra Khanong.
In addition to adorning the statue of Mae Nak and her baby, which forms the centerpiece of the shrine, with gold leaf, the faithful also donate gifts of clothing to her ghost (she has a collection of fine dresses hung behind her statue) and toys for her child. There are stalls at the shrine selling toys if you should wish to make an offering.
The story of Mae Nak Pra Kanong has been the subject of numerous films, television series and printed media in Thailand. Among the works are:
- Mae Nak Phra Khanong, a 1958 Thai film
- Nang Nak, a 1999 film by Thai director Nonzee Nimibutr
- Ghost of Mae Nak, a 2005 Thai film by British director Mark Duffield
- Nak, a Thai animated feature film, released on April 3, 2008.  
- Mae Naak, an opera composed by Somtow Sucharitkul. It was premiered in 2003 and revived in 2005 by the Bangkok Opera, with soprano Nancy Yuen performing the title role in both productions.