I think the question you are asking is is the monitory requirement reduced if you are married. For the OA or O based on being over 50 then the answer is no.
If you opt for the non immigrant O then the financial requirement is 400k only for 2 months before you apply.
I see exactly how you would come to that conclusion as I have come to the same. It doesn't help that there appears to be a glitch in the Facebook software that doesn't always show who the moderators are.
of course they can deny you boarding. Airlines have access to the database of all banned travellers. Some will also refuse boarding if you don't have onward travel within the time of your right to remain.
, if you do change to an O-A you must extend at least once on the reason you applied for the visa which will be being over 50 years of age (retirement). This means it will be 2 to 3 years before you are back to extending for reason of being married to a Thai national.