and it might be cheaper to get the visa.. Not sure.. But it could be easier with just an extension depending on your local thai embassy requirements. As said, some require bank statements.
You can extend your stay while here in Thailand. One time, for 30 extra days. For 1900 baht per head at immigration here.
Or you can apply for a tourist visa for the adults, before coming here. (Adults being anyone over 16 yo) anyone not adult, will noy get fined for overstay so they are fine, and will just get a stamp in the passport when leaving saying they overstayed.
Don't remember what a tourist visa cost, and requirements is different from embassy to embassy. Some required bank info fo4 example.
Easier just to extend the adults visa free entey when already here.
Reason for them (the airline) demanding a return ticket for no visa or tourist visa is that they are responsible for trafficking you home if denied entry into Thailand of thai immigration.
It's only the airline that will give you grief about it too.
Immigration in Thailand won't ask when you go through passport control.
No return ticket needed when you hold a non o of any kind. Or non b, or non ED.
Only if you are not having a visa at all (visa exempt) or at times on a tourist visa too.
If you get any grief from check in counter. Point out that you have a valid non O. Which means you are not a tourist, and not having to go back in 30, 60, or 90 days.
Unless you apply early, up to 30 days most places, then you would of course be able to leave within the timeframe of your current stamp and come back. But not after that and during thw 30 day under consideration, without it's own permit
that last part is not correct. The re-entry is only valid for the current stamp, which have expired during your "under consideration" stamp. The "under consideration" period is part of the new year extension. So any re-entry permit you already had expired on the date your last extension expired. You will need a new re-entry for the under consideration period. And then again a new one for the remaining 11 months.