In fact the main reason why I want to move to the other laboratory is because I am unable to concentrate on my work in this lab, this peer disturbing me all the time. I think the professor also understands it to some extent. Yesterday I spoke with him, and he gave me permission to concentrate on courses and PhD topic now, and coming to lab at later point.

Looks like he wants me to sit beside him at any cost, and keep troubling me :)

I tried changing my sitting place (as my PC had a problem), looks like he is unhappy. He made all efforts so I get back to my seat behind him. Recently I couldn't go to the lab for some time due to health issue (with permission from professor). Yesterday went to the institute after a few weeks. That peer saw me on road, and forcefully came behind me to speak to me, though I was trying to avoid him. He behaved initially like a gentleman. Enquired what problem I have. Then told me another peer is coming to the lab and coughing like me. Also told me I should not attend courses, and sit in lab.

He is a passive aggressive bully. When he sees I am good with others, all of a sudden he starts behaving very nicely and try to be my friend, and as soon as he sees I have started talking to him normally, he starts misbehaving. And his misbehaves are increasing with time. Earlier he used to keep normal distance. Nowadays he got so desperate that started physically hitting my chair!

Accepting the answer. However it does not work with the peer. I have tried reasoning out with him once. He started fighting, behaved as if he is very upset on me, stopped talking to me for 2 weeks, until he got a teaching assignment and had to work with me. He also tried to isolate me from other peers. Told (I don't know what) to all other peers around, so people were coming to talk to me when he is not around, and as soon as he enters the lab, people became serious, and moved back to desk).

Payment is not professor dependent. It is from the institute.

@MisterMiyagi, that makes sense. I am fine with completing old things, but I am getting new workload. Whatever teaching responsibility the jealous student is denying to perform and asking to assign to me, prof is assigning them to me. Also I used to mentor some junior project people when they came new here, those people are calling and demanding me to be in the laboratory to still guide them saying they got a lot of work. I don't want to perform these extra additions. These people do not know though that I am no more under prof.

No, I am not ranting. I have friends to rant. I have given all details so the full situation is clear. I am asking for advice on my next step. With no reply, is it ok that I start working with my new advisor for my PhD topic? Or do I meet the other professor personally and ask for permission again?

Thanks. I cleared the air. He laughed and seemed a bit unhappy with me. I guess it will be ok in the long run.

Yes, probably it was not clear in my first mail, but I clearly mentioned it in my second email. But no reply .. Any idea on how to amend this situation now?