Can I apply for two Non-O visas, one for myself over 50 and one for my wife under 50, while living in Thailand?

The only way to do it is when you're in your home country, the over 50 spouse applies for the non-O for over 50 and the under 50 spouse applies for the non-O as a trailing spouse. A lot of embassies no longer offer this option though.

Some might offer it but only if the older spouse has a non-OA and not with the non-O.

Regardless of what is possible, if you're going to be using the Thai embassy in Paris you're probably screwed either way. We've received nothing but terrible reports about that embassy. They take multiple months to process visa applications and love to deny applications because the dates of travel that was submitted with the application already passed because they took so long.

Always was impossible to get in Thailand, now all nearby embassies have also stopped issuing the trailing spouse visa for someone on a non-o retirement visa. Most western ones have also followed suit