Hi Saurabh,
I just had my second hair transplant with Dr. P a few days ago.
He does a great job and I was very happy with the first but just wanted the density increased this time. His staff is very good as well.
Don't worry about the $1000 USD deposit. It's completely legitimate and the reason he asks for a deposit is to make sure that you show up for your appointment.
Good luck with your transplant. You are in good hands with Dr. P. So much so that I went back to him for a second time and when my crown starts to thin, I will likely go back to him for a third procedure as well.
Also, Bangkok is a great city. Make sure you go for a foot massage, do some shopping at Patpong and MBK, and if you're there for the weekend, stop by Chatichuk Weekend Market; just be careful not to bump your head if your are out exploring the city after your transplant.
Cheers man, and good luck