the moderators and other contributors on this forum give reasoned and knowledgeable advice, then the occasional one turns up, gives opposite advice from the moderators which confuses genuine questions , you appear to be one of those people.
as pointed out by many on this forum, it’s hit or miss whether the airline or immigration ask, but if they do you have to purchase POOT on the spot, if you don’t have evidence, before either gaining entrance aboard a flight or through customs, is happened to thousands of people, I have probably only been asked 10% of the times I’ve traveled to Thailand