It shouldn't be a problem to find a thai prostitute with beautiful long hair.

Go either to Nana Entertainment Plaza or to Soi Cowboy. I would expect that the lady of your choice will be surprised if you tell her what you exactly want, however if you offer her a good tip she will probably agree.

I can't tell you what the ladies in BKK actually charge as I always go to Pattaya, probably something around THB 2,000 for a short time and 4,000 for long time. In that case I would increase my offer by around 1,000. Certainly it will be possible to get it cheaper, however as your time is limited you better don't waste it with looking for a bargain.