@Kevin *********
I've heard stories where this has happened. It's pure racism and those practicing it should be sued. If a Thai passport isn't even enough to get the proper Thai price, you know it's because Thais are jealous of farang and they see everything in terms of race. This explains why a CAMBODIAN who is by definition a foreigner can get the Thai price without having to prove their "credentials" but a Thai citizen, sometimes including Indian-Thais and Eurasian Thais (those of mixed Thai-European parentage) both of whom may have been born in Thailand, get charged the foreigner price.
There would be riots if that happened in America. Think about it.
It's very much like the Jim Crow laws. What's next, special seating on public transportation for foreigners, separated from the "clean" Thais?