Keep flirting with him subtly, and smiling at him. If he is super funny, joke around with him.
Some guys don't like the girl to ask him out.
Just ask him out. You don't have to wait for a guy to ask you out. The worst he can do is say no.
If you like him, why don't you ask him out? Can't take the social pressure? This is not the 20th century any more. It's OK for a girl to ask a guy out. Do you fear rejection? Use your words -chicken...