Each city and town in Thailand has a few differences, just like any city or town in the USA of how certain bars and massage parlors are operated. Also, Depending upon where the girl is from can make a big difference in how she acts, what she knows and what she will do to survive working at her job.
Lets take Phuket for example. The women overall I found in Phuket are somewhat larger in body size than the girls in Pattaya. They wear alot more makeup in Phuket and their complexion is not as nice. I've noticed more girls smoke in Phuket than other places.
The Phuket massage girls are not as sex crazy as they are in Pattaya also. Its not as common in Phuket to have sex inside the shops as it is in the Pattaya shops.
The biggest observation I've noticed about the massage girls is that no matter where they are from or where they work, it is entirely up to the girl if SHE wants to do any kind of sexual favor for you. The shop has nothing to do with her sexual performances. If SHE feels uncomfortable having sex with you in the shop, she may suggest taking her back to your hotel, room, apt., etc.
This goes for all places in Thailand. Sex is entirely up to the girl, contrary to certain people that think otherwise.
Bangkok would be an exception where if the girl takes a job in one of the upper class massage places, they will be told that sex is to be offered to any guy who comes into their parlor. So, if the girl has any reservations about this policy, she does not take the job.