In my opinion, the dual pricing is unconstitutional. I am a Thai citizen, but I don't necessarily look Thai. I am often overcharged at hospitals (and other places) just based on my skin color. From my perspective, this seems both racist and unfair.
In most cases, once I push the issue and show my ID, I am often given the "Thai price"; however, I have also been told many times, "you look western, so you can pay more", even after showing my ID card.