@Luit ****************
they put it to the airlines strangely enough to protect travelers. If airlines wouldn't pre-check entry eligibility, nothing stops the Thai authorities from still doing that and just let people fly back. But that's an expensive joke; the airline will charge whatever they want and if you can't enter Thailand you have not much of a choice but paying (or even taking debt).
So the intention is good, but it puts airlines in a aan uncomfortable spot. Obviously they cannot refuse a paying customer who is eligible to enter. As the fines that countries impose take away any room for the opposite error, they don't have room for any. They must always make the exact right decision. Travelers however are less likely to step up for their right, so in case of doubt, it's understandable they go for the refusal. So a measure that aims to protect travelers actually makes paying customers who are eligible to enter getting refused boarding.
Travelers are required by the airline's terms and conditions to take care of their own entry eligibility anyways. So the waiver could solve the above challenge. If they'd do this more often and consider the pre-check on entry eligibility just advisory, then all those unjust refusals could be a thing of the past.