My wife is Thai, and I manage to speak thai a bit. I took several months of thai lessons. I confirm what has been said before. There is no yes/no word in thai. Those examples on those sites are just bad translation for beginners.

For example the word "chai" that they give for "yes" is more close to "true" when you agree with what has been said.

"Chai" is just a particular answer that can be given to a particular question. You can't use it as a "yes" answer to all question.