1. 拳 (kwun): This is the most common and general term for "fist." It's often used in martial arts contexts.
2. 握緊拳頭 (wat gan kyun tau): This translates literally to "grasp tightly fist head" and is more specific to the action of making a fist.
You can choose which one to use depending on the context. For example, if you're talking about a punch, you would probably use "拳 (kwun)." If you're describing someone making a fist, you could use either "拳 (kwun)" or "握緊拳頭 (wat gan kyun tau)."