So, do you think this kind of behavior is still considered normal, or is it something to be concerned about?
It may be “normal” today in the sense that it does not cause him problems because he only spends the money he can afford to lose and it is an entertainment for him, but someone who has no social life and whose only hobby is gambling online has all the chances to end up very bad in the future. Let him go out, see the sunlight, interact with real people, interact with people of the sex he is attracted to, and then if he wants to spend some time gambling it's OK, that would be a better plan for normality.
You're right, though I'm still having a doubt about this issue of not having any other hobby apart from gambling. You know I have an idea of a gambler who spend alot of time in playing gamble and as well other internet business, but this does not stop him from coming out to get in touch with people and also spend time with them. Though what op said might be true but I think this case is very different from the ones that I have been seeing. Just as you said earlier that so far as he's comfortable with it, and also not being addicted to it of course that's what matters the most.
Gambling is a game that if a normal person plays regularly for a few days, he becomes addicted to it by about 70%. And if someone likes gambling only, then I can say that he is completely addicted. It is most important not to get addicted to gambling, but the game is designed in such a way that you will be bound to get addicted. So I can say that if your only hobby is gambling, then you will definitely get addicted.
Anyone who choose gambling as his hobby will definitely get addicted to it, and there's no two ways about it. Because there's no way that you can escape from being addicted to it, you know once you keep gambling more often it will now become part of you and once this happens it means one is addicted into gambling, at this point you will be finding it very hard to stop. is obvious that gambling is part of fun and entertainment but even as that we shouldn't consider it being a hobby.