M.P.
This sounds like a major change in his behavior. Stealing and getting suspended are starting the misbehavior at the top of seriousness. What did he do to get suspended? I suggest something serious is going on with your son and you need to find out what it is.
Have you talked with him? In a calm non-judgmental way? This is the first step. Also talk with the teacher and the principal to find out what their take is on his behavior. If he hasn't seen the school counselor arrange for that to happen. If doing these things doesn't get to the reason why and/or stop the behavior it's time for a child therapist.
It's important to deal with this without anger. Being and showing anger to your son will shut him down and you won't learn anything. Try to understand why he feels that he needs to steal. Be compassionate while remaining firm about this behavior ending.
Punishment doesn't work as well as discipline. You have to know why he's doing this. Discipline is teaching him that this behavior will not get him what he wants in the long run. Give him logical consequences related to his behavior. For example, for stealing have him return what he took and apologize to the owner.
I could answer more completely if I knew more about his behavior. Who is he fighting and why? What did he steal? Why was he suspended?