Can I use a 90-day Non-O spouse visa in Thailand annually for three months of the year?

You didn’t need to go to immigration to get your stamp moved into your new passport. Simply show both passports when exited Thailand and they would stamp you out in the new passport. Same when you came back in. Just show both passports along with the print out of you visa, and the IO will put the new 180 day stamp into you new passport.

The 180 day stamp is not your visa, is just the stamp.

Also you would not have been pulled up about failing to do the 90 day report at the airport or boarder crossing.

As for trying to extend the 180 day stamp at immigration in Thailand, forgot it. Much easier to go out a of Thailand preferably for a short holiday and back in for 180 day stamp

Shorts! Definitely not for government appointments.

Since when are shorts an issue? I understand flip flops. But shorts? Im fairly certain immigration wouldnt be pleased with me dripping sweat everywhere from wearing long pants.

Why extend it? You have many years left, and just leave thailand and come back to get 6 more month. Extension is done end of period 5 years later.