Is my best buddy bi or not? Please help me.?

I am 21 year-old straight guy that lives in an asian country where we are not so liberated as the other western countries. So I have this buddy who seems to be a straight guy, he likes to talk a lot with different kinds of people, he sings and dances well, he is my calculus instructor by the way, but he's one of my best buddy now. He plays basketball too but I think its not his pion, he seems to be very straight guy when you look at him. my concern now is that we've been very close for about 2months only. so whenever we are with our group of friends, he seems like to be a normal guy. But, sometimes when we are together I feel like he stares at me differently, like there is something? I feel like he likes me or what, Most often when we got drunk, he really often stares at me like he is trying to say something gayish?? Often times when we get to stay in our other friend's house, when we're about to sleep or while we're sleeping, he often stares at me sleeping, cause I cant sleep so I have to move into other position and I would see him staring at me,. another is that he admitted to me that he had 3 non-serious girlfriends way back when he is still studying and that he is a virgin.. so that reason makes me think that he is biual.. although my speculations are not yet firm.. I just want to know if he is or not. it's fine with me with whatever he is. Please give me what you think about this.. thanks a lot for helping..