A very very long time ago I stayed in a quite new guest house in Chiang Mai.
The price was 80 baht a night.
I fancied one of the receptionist so hung out in the lobby quite a bit.
One time some Thai people came in and ask how much for the night.
The person on the desk said 120 baht a night.
After they were finished...I pitched up and ask .How come you charge them more.The reply "Oh Thai people would think room no good ,dirty for only 80 baht.
Double pricing works both ways .