I agree with Mark that this is completely disrespectful and I really dislike it when players behave this way.
That being said, I totally disagree that you should assess a technical foul for the player not responding to you. Doing so is only going to put ALL attention on your behavior rather than the player's.
If he is that much of an idiot, just wait a few minutes -- I'm sure that he is going to do something else stupid! You are doing him a courtesy for warning him about crossing over the boundary. If he ignores you, fine -- just call the tech for reaching over the plane rather than unsportsmanlike. If you just issued the warning and the player performs the same action again to receive the tech, what is the coach going to say?
I always try to identify the one or two PABs on each team and it's usually pretty easy to figure out who they are within the first couple of minutes. The challenge is to figure out which PAB belongs to which idiot parent in the stands
