Thai Buddhist tradition tells of a monk named Phra Malai, renowned for his accumulated merit and his powers of meditation, who is able to travel to realms ordinary beings cannot reach. Moved by compassion, he descends into the various Buddhist hells, where he witnesses beings suffering the specific torments their past misdeeds have earned them, and offers what comfort he can, encouraging them toward the good conduct and the accumulation of merit that will eventually allow their release into a better rebirth.
Different regional tellings of the story vary in how much detail they give of the hells themselves and in exactly which categories of wrongdoing are shown being punished there, reflecting the tale's long life as a living oral and performed tradition across Thailand and neighboring Lao-speaking regions rather than a single fixed text; Bonnie Brereton's study collected more than a dozen distinct textual versions circulating within Thailand alone, none of them treated as more authoritative than the others in ordinary devotional use.
The legend is generally traced to Pali and vernacular textual traditions that developed across mainland Southeast Asia, with Phra Malai himself sometimes described as having lived in Sri Lanka before the story spread and took on distinctly Thai and Lao regional details, including local place names and locally specific descriptions of the hells, as it was retold and copied by generations of scribes and monks across many centuries.