Ha ha. This has to be the number one question on every female forum.
I have had several horror jobs here, but a couple of really good ones too.
I have been going to the one on the first floor (2nd to Americans) in Silom Centre and have had two good haircuts there, both from men, and one awful one from a woman.
I think you have to pay a bit to get one who can understand what you want.
I'm sure there are plenty of good hairdressers in the small shops but if you cant tell them what you want, you could get anything.