Isolation.
If it is only two, separate them. Use a wangta chair: Put a chair or desk near the back of the class in the middle of the floor away from most of the students. When the student refuses to obey the Korean teacher or you and immediately starts acting up, make them move to that chair. Leave him there for a short time or long time depending on how well you think he'll behave once back in his seat.
Do this consistently for several classes, and it usually has a positive affect.
Every once in awhile a student won't take this seriously and jokes around when being moved. Usually, my angry face and quick snap like saying "NOW!" is enough to show I am serious and angry.
If it is a really bad student, I'll move the student into the hallway and make them stand there for a few minutes. (no extra punishment other than leaving the room with me.)
If it is a really bad student causing too much disruption, you can take him down to his homeroom teacher. That is like being sent to the principle's office in the US. They really don't like being taken to their homeroom teacher. I've only had to do that a couple of times during the first semester. I think it helped with discipline with the rest of the students who saw that was one of the weapons in the discipline arsenal.
Some students will never participate in class no matter what you try in a full-class environment. The best you can do is prevent him/her from disrupting the ability to learn of the rest of the class.
If isolation doesn't convince them it is better to cooperate than ignore being told to pay attention, it will at least keep them from harming the activity for the other students.
