In general there’s no requirement of mandatory time or days in Thailand to maintain a permission to stay as long as you’re back in time to apply for a new extension and the 90 days report is just suspended while you’re out of Thailand. This is for yearly extensions of stay with re-entry permits, -not the initial one year visa.
Makes no difference unless you’re married to a Thai national. Ore else both need to qualify individually for a Non O based on retirement. You can find more information here. You probably can bring a parrot as long as all vaccines and registration with official vet authorities for pets in general is completed.
Best option is to apply for a Non O e-visa based on retirement online before you leave for Thailand. Can be applied for up to three months before you plan to leave.
Pointless to hold a visa before you are leaving. And there’s no mandatory time you’ll need to stay in Thailand to maintain your permission to stay.
These are anyway the formal rules for entering Thailand as a tourist. Random checks are done and it is up to the each and everyone how they want to deal with this.
If it wasn’t a formal requirement the airlines wouldn’t care. But they are required to check if the passengers fulfil formal requirements and can get fined with 10 000 USD and be responsible for your return if the immigration ask and potentially deny a passenger.
You can only do one extension unless you’re married Thai or have a Thai child. Best option is to get a six months multiple entries tourist visa before you come in order to avoid going back to back on visa exemption.