In the past few years we have been denied boarding by the airline. They won’t budge. So just spend the $40usd and get a 60 day tourist visa before the flight. Then there will be no problems.
A few years ago I had a similar issue. And after much digging (not on the first or second page) the TAT confirmed that you needed 6 months min in your passport from the date of entry. And the airline was the one that put up the first road block to getting to Thailand
Google the document needed. From the USA you must have a notarized document signed by both parents authorizing you to take the minor out of the country. Plus I would have a notarized POA for health care needs also. Cover your bases. You don’t want a nasty surprise somewhere. A local attorney could make sure you are doing it all correctly also
Last year I had a 60 day visa with the intention of getting the 30 extension. The airline refused completely to let me board. I took it up the food chain. I bought a one way ticket out of Thailand departing on day 59 - it was cheap on airasia. Then they let me board. The 60 day visa was worthless for boarding the flight