I just wrote an article about how there are so many miserable expats in Thailand and I don't understand why they stick around. Well, this is another thing that really sets people off here and for the most part, I agree with the notion that this stuff kind of stinks. The Dual Pricing system of charging foreigners substantially more for things gets old, especially once you learn to read Thai.
The Thai numerals are almost never used anywhere. No one defaults to them as the Western numerals were adopted a very long time ago. They do still have their purpose though, and the place you see them most often is in tourist areas where an entrance fee is required.
The above sign says that adults are 20 baht in Thai and 200 baht in English. Some older signs had both sets of numbers in western numbers, but obviously this caused problems.
This is somewhat justified by saying that the foreigners do not contribute to the taxation that leads to the funding of these parks and that is a clever way of making money off of racism with impunity I suppose. The real reason it is done is because they can do whatever they want and you have no choice but to deal with it.
It is a bit of a shame because it kind of gives visitors a bad feeling when they find this out. They start to feel like a sheep that was meant for fleecing. It just kind of leaves a horrible memory about something that would otherwise be wonderful. It still is wonderful but recently in Krabi, they changed the already absurd 10x the price that foreigners were paying to access marine parks and changed it to 20 times the price. At this level, you can no longer say anything about taxation, this is simply greed and you know it.
It isn't just the government, it is private institutions as well, such as this noodle shop
source
The Thai script says the soup is 50B
out of principal, i will not visit a restaurant that charges two sets of prices based on the color of your skin.. that would be extremely illegal in other parts of the world. I don't want a law passed or anything because I hate the government for the most part, but I will not reward any business for doing this. There was a small rice shop I had been visiting for years in Krabi, and then I found out by overhearing that the Thai people were all being charged less than me. Without causing her to lose face I told the woman that runs the place that I heard what she said and I will never return. She then tried to tell me that "you can have Thai price" but at that point I don't want it.
So while this is definitely something you will encounter in this country, I don't think it is worth getting all worked up over and complaining about constantly. Normally it is just a small thing unless the government is involved. You do have to know how to speak Thai a bit to figure it out. Sometimes I wish I hadn't learned and then could be part of the "ignorance is bliss" segment of society.