I don't believe anyone said that. The subject of the thread is what a customer's options for redress are given a situation where he or she is denied boarding. What you are talking about is really a different topic: what customers can do beforehand to avoid being denied boarding in the first place.

As I pointed out, requirements for entry into the Kingdom of Thailand for U.S. citizen visa-exempt tourists are determined by Thailand's Immigration Bureau. Not the U.S. State Department, not Thai Airways, not the Thai Ministry of Foreign Affairs and, yes, not Timatic. If the airline in this case is going to withhold a refund or some kind of compensation, it should be asked to document and prove that U.S. citizens really do need 6 months on their passports under the actual published set of rules and directives implemented by Thailand's Immigration Bureau. Or else it should show that customers were explicitly warned in advance that they would not be allowed to board with less than 6 months left on the passport (which does not appear to have been the case here as the computer system initially said everything was fine and the OP received a printed boarding pass).

If they cannot prove that the 6 month rule exists for U.S. citizen visa-exempt tourists, they should be prepared to apologize and offer a refund and maybe a good-will upgrade or voucher.