According to most accounts, the phi kra-hang has the appearance of a flying man with two rice trays for wings with a pestle for tail. Some less common accounts say it is a feathered flying man with a bird-like tail who should NOT be confused with the kinnali or kinnon.
Some believe it to be someone who has become skilled in the use of magic and can now grow wings and fly. Others think it is someone who wronged a teacher, especially by breaking a promise to one. Another possible method is from eating certain gourds or walking under a bridge, but this isn't considered a very common way to become a phi kra-hang.
Upon finishing his transformation, according to the more common accounts, he now uses two circular, normally used for sifting rice, as his wings, and a small pestle as his tail held between his legs. You can see one depicted in the classic Thai light bulb commercial:
The preferred diet of the phi kra-hang is filth, but other than that, little is know of its ecology and habits. Some say it's touchy about people touching his behind, for fear of his true nature being discovered if you see his stump of a tail. There are some accounts that connect him to the krasue, but this may be a stretch. A few claim these beings are restricted to central Thailand for the most part.
There is some dispute as to whether he hurts people, or is merely ambivalent towards them. Most consider it a phi to avoid in any case. There are accounts that at night, he gives off a glowing aura. But of course, it might be a different phi in the shape of a phi kra-hang. You never can be too certain with this sort of thing.
What stories do you know about the phi kra-hang?