Should I ask my friend for money back in front of everyone?
Are you serious? Why are you going to embarrass him like that?
I hate people who can't pay their debts.
I understand that public humiliation is a valid tactic, but it's very degrading to the other person. You need to do this in private, so they are treated with dignity and not like a clown showcase. Your friendship is worth more than this.
It should be okay since if he wants to keep the group together, he has to pay it back. If he doesn't, I'll dump his ass.
Even if he pays it back by putting him on the spot and embarrassing him like that, it will make you look very bad and others might start to wonder if you would do the same to them. I think you should still conduct this privately to avoid any kind of drama. It might better for your own reputation.