After 60 days you can apply for the 1 year Extension of Stay based on being over 50 years of age (retirement visa) and when this 1 year is stamped in your passport you can apply for the mutliple re-entry permit, with that permit you can go and come back using this year until the last date.
There are multiple visa and an Extension of Stay all called retirement visa, to make things complicated.
With the Non Immigrant O visa based on over 50 years of age (retirement Visa) applied for in your home country gives you 90 days of stay inside Thailand.
No, only during the 2 months prior application and at request of the Immigration Office during the 1 month under consideration. Rest of the year you can spend it all.
If you have a new 1 year Multiple Entry Non Immigrant O visa, that means you are only allowed to stay 90 days inside the country, than leave and come back before the valid until date to get a new 90 days stay.
For combined method, the rules seems to stay the same, for at least 3 months after application the full amount and the rest of the year not less than half.
As you apply for a new Extension you must have at least 2 months prior application the 400.000 Thb on the bank or use an income affidavit from your Embassy, or if they do not provide, at least 12 months prior application a monthly foreign deposit of at least 40.000 Thb into your Thai bank account.
If you get to the end of your Extenion of Stay based on being over 50 years and want to apply for the new Extension of Stay based on marriage with a Thai National, you need to keep two things in mind.
You promised to keep 800.000 Thb for at least 3 months after you got the Extension based on over 50 years on a Thai bank account on your name and the rest of the year not less than 400.000 Thb.
You can use the same bank account as there must be 400.000 Thb on that bank account for at least 8 months.
The Hospital who told you to go into quarantine due to covid is the place to ask, not your landlord, not your insurance agency, not the nurse working for your condo complex.