my hubby and I came to Thailand on a STV from Australia early March.
Accommodation- we provided multiple Agoda bookings, direct hotel bookings and Airbnb to cover the first 90 days. No issue having approved via Canberra embassy. (Unless you live in NSW we were told we had to use Canberra embassy )
Last extension needs to be applied by Sep 2022 (currently) so depending when you arrive you may not be able to obtain your 2 extensions.