you didn't answer my question. Are you were a Thai resident and you were denied the miniscule discount? You're right, it does sound like "Jim Crow" white elitism.Think of it as being a surcharge for yourself being so superior.
Thais already pay taxes that subsidize the parks, why should they pay more than you by paying twice? Disneyland has discounted park entree fees for instate residence with drivers license ad well as state camping parks in America. It's no big deal.