I am a Single guy and do get non-sense ideas when a girl smiles at me. My mind will start thinking the girl likes me and she is interested in me. Sometime the name of the girl keeps playing in my mind. In reality they don't know me or care about me. But my mind keeps bombarding with these thoughts. I understand it can be due to Lust also.
How to overcome these thoughts and treat them as my friend and sisters
Are you talking about a girl you know in a social or professional sense, or something more like when a girl just happens to pass by and smiles at you?
It's perfectly natural for a guy to feel good when a girl (especially a girl you find attractive) smiles at you. Sometimes it doesn't mean anything. Sometimes it means she likes you. Maybe she would like to know you better..
As for your feelings about it, they are normal. If a pretty girl smiles at you and you think "hey, she's kinda cute" and smile back, there's nothing wrong with that. If you wonder whether she might be interested in getting to know you better, there's nothing wrong with that. If you get talking with her and end up dating her, there's nothing wrong with that. If you go away and spend hours fantasising about her, mentally undressing her and the like, that's not good. If you find yourself doing that your best bet is to try and think about something else. To simply "stop thinking about it" often doesn't work but if you take the specific step of thinking about something else you can often push the less helpful thoughts out of your mind.