It also very much depends on the immigration where you want to do the covid extention. Some immigrations are not giving it as easy as others do. So it depends on your location to.
Do you need to leave your passport at the embassy? That seems not normal to me. I know many countries where you can keep the current still valid passport untill the new passport is handed out. The old passport then will be stapped invalid and or holes will be punched in it.
I know about the requirements for extention of stay. I have this already for many years. But with covid the re-entry requirements suddenly changed and last re-entry in october 2021 i had to buy a 100.000 USD insurance valid till my extension date. That was before Thai Pass. Still all who travel to Thailand have to request Thai Pass and therefore need to show a 10.000 USD covid insurance. But for how long if i have a active extension of stay (retirement) Non O.
What if i come back with a extention of stay based on Non O? Some say i only need a 1 month covid insurance for entry. For the extention i not need any.
If you not have a TM30 slip which is a small sheet of paper from.the immigration that confirms the reporting of your adress, then you can get one very easy when you visit the immigration. You might have a screenprint from your landlord already to show at the immigration
To answer your first question. Yes, with a Brazilian passport you get 90 days visa waiver. It is a bilateral agreement. Recently I met a Brazilian who showed me his 90 day stamp.