How should I interpret this and how to behave when I see him next time?

[Cute1111]

At our first bumping into each other I couldn't smile although he was smiling. Then first time I saw him, I said hi and he said hi too while smiling. But, later when we met, he passed in front of me, i was looking st him but he even didn't look at me..

[SueShe]

If he smiled twice at you and you did not show any kind of emotions, then he probably though you are too serious of a person to bother and then kind of gave up on you and trying to pick you up or hit on you.

Basically, when a guy smiles at a total stranger, mainly if that stranger is a girl, it is for a very specific reason. You obviously did not react the way he expected and then he did not insist and passed you without looking or smiling at you, knowing that he was wasting his time trying to hit on you.

Don't worry about it. I do it all the time because that way, you keep those people away from you and you don't have to bother with them.

Next time you see him, you can just say "hi" but don't hint at anything because he will think that he has a chance with you.

[Guy13]

Sometimes people have something on their mind and are in process of accomplishing what is on their mind. He was not purposefully avoiding befriending you once again. All you had to do was with your fist up against your body inconspicuously. Then, next time you saw him, "why did you not wave back... with smile"-Then, you would have discovered what was on his mind... over coffee perhaps.

[jshm2]

Move on, you're too socially awkward.

[Avicenna]

I wouldn’t read anything into it

[In_Trance]

this is nothing