If you are on the initial 90 days of the Non Immigrant B visa you can not apply for an Extension of Stay based on being over 50 years of age (short cut: retirement visa), the first extension of stay must be for the same reason as the visa is issued.
I guess you call the 1 year Extension of Stay a retirement visa, the requirement is each and every month a minimum of 65.000 Thb as foreign deposit into a Thai bank account in your name if your Embassy does not provide the affidavit of income.
So missing 1 month and having extra deposit another months is not each and every month.
The report is done when your are 90 days inside Thailand.
You left Thailand so you are not inside Thailand and the count of days being inside Thailand stopped at the moment you left.
The day you landed back into Thailand will be day number 1 and you start counting again all by yourself and make the report IF you stay 90 days inside Thailand.
If you decide to travel abroad again, the day you leave the count stops and the day your arrive back the count starts new with day number 1.
Apply for the Non Immigrant O visa based on being over 50 years of age and for the spouse the Non Immigrant O visa as dependant at the Thai Embassy in Pretoria who are very helpful and have good service.
Get 90 days on entry and before these 90 days ends, apply both for the 1 year Extension of Stay.
What kind of stay do you have and for what kind of extension of stay did you apply or what is the reason that the Immigration Officer told you when they not approved your application.
I guess you visit every year an Immigration Office with documents of the organization and get every time a new stamp with the text " Extension of Stay permitted up to xx/xx/xx" .
You go with a letter of the volunteer organzation to the Immigration Office to cancel your stay at your last day of being a volunteer and apply directly for a new Extension of Stay based on being over 50 years of age (retirement).
Make sure you meet all the requirements for the new extension before you cancel you legal stay in Thailand.