I included a Shaolin Monk character option in the Weird West RPG and as some people have noted, it's not just limited to Westerns and could be used for other OSR style games. It's actually fairly compatible with the Old School Retro Clones and similar games.
Here's the Shaolin Monk option for WW characters:
Shaolin Monk – Fighting is +2. Unarmed attacks use d6. Requires: Magic 1. Can only make unarmed attacks.
Combining that with the base path in Weird West and the slight difference to Skill / Defence, we can convert the monk over to D&D/LL/S&W/WF style rules, giving us something like this:
MonkClass Requirements: Wisdom, 13+ (5% experience)
Hit Dice: d6/level (Gains 2 hp/level after 9th)
Armor/Shield Permitted: None (see below)
Weapons Permitted: None (see below)
Monk Class Abilities
Unarmed Attacks: A Monk makes attack rolls as if they were 2 levels higher (3rd level attack rolls at 1st level etc) and roll a d6 for damage from their unarmed attacks.
Improved Defence: Monks gain a +2 bonus to their armor class at 1st level, and an additional +1 bonus at other odd numbered levels (3,5,7,9 etc).
And there's our streamlined OSR Monk Class. This version doesn't include some of the more magical abilities, or non-combat physical skills you see in some versions of the Monk Class. Some suggestions for those are also in the Weird West book, so you could build an alternate Monk to fit your campaign if you like.
I compressed a lot of rules into the small(!) page count for Weird West... but if you want to uncompress it out for use in other OSR games I think it's reasonably straightforward. :)