Monk absolutely can't tank. They don't have the enmity generating abilities to do so, not to mention the lack of health. At most you can get a monster's attention if things turn sour but not for long.

Pugilists, maybe. You'd have to cross-class a lot of stuff and even then you wouldn't come close to Warrior or even Paladin.

SE has enough trouble balancing Paladin and Warrior, let's not throw Pugilist back into the mix. They turned PGL/MNK away from tanking for a reason. PGL used to be able to tank but they took all of those abilities away and left us with Taunt which amounts to a few seconds of max hate.