its because lots of thais do this to not only in usa but in other countries like Korea for better pay. They are considered high risk for overstaying statistically.
I am chinese/thai but born in thailand. The reason they do not like chinese people from china is because there are chinese who look down on other asian countries but like to visit those countries because they are cheaper. My time in Thailand, I personally witness Chinese people who would walk to the front of the line and just cut in when the line starts moving. They would act like they are just standing there to talk but really they are waiting to cut in line and the thais are too nice to say anything. They bump into you and dont apologize and walk off like nothing happened. These are personal experiences and it is why thais do not like chinese tourists because they dont know if these chinese are going to rude or not. They arent being racist but statistically its the chinese tourist who are more likely to be rude.
Anything over 10 grand raises questions. And if you have a child with you and you have over 10grand in a car with you and your children, trust me when I say that it is a danger to yourself and kids. As such, if caught, you have a chance to lose your kids. Each state is different but in texas, you will lose your kids. It happened to a friend so when you talk about money over 10grand it is universal that anything close to that amount or over raises questions and has consequences. Even transfers over that amount gets flagged in your bank account and the irs will start snooping.