The Monk is a Fighter, with the following special rules:

• AC is 3, unarmored.
• Attack is 1d6, unarmed.
• May use any object that she can lift as an improvised buckler, for AC 2.
• May attack with any object she can lift (1d6 damage); the only advantage to this is not actually having to touch the target (in case it’s on fire or is an ooze or something) and she gets the reach of the object (if you’re using rules for reach).  The Martial Artist isn’t subject to the penalties for the size of the object (if you’re using those) as long as she’s not using the extra reach, since she can just change her grip to not use it at full extension.
• May not use missile weapons, or ordinary weapons except as improvised bucklers/ways of extending reach (i.e. doesn’t get additional damage if using variable weapon damage rules, doesn’t get bonuses for magic weapons).

That’s it.  You’re encouraged to also use “Super Simple Combat Maneuvers“, to give the Martial Artist more variety and the chance to do take-downs, holds, and the like.

If you want a Martial Artist with Esoteric Chi powers, you could base it on an Elf instead, and adapt the spells to chi powers, but that’s for another day.