Bouzu The Clowns.
There are a ton of Yokai that disguise themselves as monks. First we had the Char-Monk, a floundering fiend.
Here is the 大坊主 (Oo-Bozu or Giant Monk) from Inaba in Totsutori-Ken. I couldn't really decipher much more than he exterminates Samurai and is taunted by Shopkeepers (or taunts Shopkeepers-I'm not sure which.) Pretty cool looking, has kind of a Basil Wolverton thing going on.
The ざしき坊主 (Zashiki-Bouzu or Tatami-Monk) is another Monk who likes to murder but I can't find much else about him. (This guy seems to have a Charles Addams thing going on.) Even so, I think he shows up in this 'Tube but even if he doesn't, it's pretty damn cool!
A lot less human looking but a lot frightening would be the 海坊主 (Umi-Bouzu or a Sea-Bonze). Umibōzu is said to live in the ocean and capsize the ship of anyone who dares speak to it. This spirit's name, which combines the character for "sea" with the character of "Buddhist monk," is possibly related to the fact that the Umibōzu is said to have a large, round head, resembling the shaven heads of Buddhist monks. Alternatively they are enormous Yokai that appear to shipwreck victims and fishermen. They are believed to be drowned priests, and exhibit the shaven head and typically appears to be praying. It is usually reported as having a grey, cloud-like torso and serpentine limbs.
(Does anyone else wish that these had English Subtitles? They are terrific.)
白坊主 or Shiro-bōzu is a white, faceless spirit from Izumi. Scroll down here and take a peek at the ghosty-thing in the purple kimono.
Bouzu-Tanuki) who appears to be a Monk in the guise of a Tanuki. He doesn't seem overly evil or nasty, just a bit of a trickster.