I would say never pay more than 10 baht inside the usual Pattaya bus loops. I maybe overpaying at 20 baht to Jomtien but the one time I asked of course the driver said "20 baht". If you ask a driver to take you somewhere specific you are looking at 100 baht. Sometimes I wave a bus down at some location where he might have an option of turning two ways. Say you are south of South Road on 2nd Road and want to go to Jomtien but the bus could go to Pratumnak Road instead. After waving I point off to the left and if the driver is going to Pratumnak Road he will pass me by.Sounds like it's not as cut and dry as i'd thought.
Any Thai with a farang is usually expected to pay 10 baht. I have a friend from Canada that lives here with his Thai wife. Sometimes three of the wife's family come and visit and every trip on a bus for the five of them costs him 50 baht. Another good reason not to get married.I think the local Thais pay 5 Baht, unless they're a bar worker accompanied by a Farang.