@Antony *****
, as people said she's not gonna be able to switch passports by land and she'll be required to follow the quarantine rules in the country she'd be going to by air as well as following the quarantine rules in thailand when she comes back IF she flies out and in.
I don't know why Chaengwattana told you she needed to go to her home province to get the year extension on her Aussie passport (unless you guys aren't registered to live in Bangkok) BUT that'd be the easiest thing given the covid-19 stuff going on now.
There's minimal documentation required and they'll give her a year extension for 1900baht. THEN later this year once the places start opening back up you can decide what to do so she can exit the country on her Aussie passport and re-enter on her thai one.