Your story a lot of gaps. Why Ah bengs want to attack your
friend? Is it to extort money? If not, don't tell me they attack
him for no reason? Your friend may have prior dealing with those Ah
bengs or he may have earlier provoked them.
Moral of the story is, if somebody slap you on your left cheek,
you offer your right cheek. You don't punch him back. If somebody
threaten you with a knife. You give them the money they ask for and
then report to police. Or alternatively you run. If somebody call
you names and insult you, you punch them? No. We live in country
with laws. We must abide by them. We got police and their job is to
protect you, so if you are threaten then you call the police after
that. But for your "friend", too late. Now he has to pay the price.
Will he learn his lesson? It is all up to him not to repeat this
again.