Sometimes the "gatekeeper" can be an over-zealous airline employee
Yesterday I was almost denied boarding to BKK by a young airline check-in counter staffer who didn't have a complete grasp of Thailand entry rules.
He argued that my Non-Imm O, granted by the Thai Embassy, was unnecessary and questioned why I wasn't entering as visa-exempt/VOA. He didn't believe it allowed for 90 days upon entry and demanded proof of onward travel (luckily I had it, just in case something like this happened). He then scrutinized that ticket with apparent disbelief for several minutes, and had to confirm that Don Mueang was an actual airport. 🙄
Finally, he questioned the legitimacy of my (6+-years) marriage to a Thai national and wanted to see proof of that.
As you know, if he had denied me boarding it would have affected several other time-sensitive permits/forms.
I was adamant and stood my ground, and eventually another airline employee (maybe his supervisor) got involved and he quietly issued my boarding pass without further comment or apology.
Even when you have all your paperwork in place and t's crossed, a low-information airline ticket agent could throw a wrench into your plans. 🔧