If you don’t have any issues with parking 800K or 400K baht in a Thai bank account, a Non O visa and yearly extension of stay with re-entry permit based on being retired (passed 50 years) or married to a Thai (If that’s the case) is probably the best and most common option.
If you don’t want to park any funds in a Thai bank and don’t have any issues with a Thai health insurance, a one year Non O-A multiple entries visa (which gives up to two years stay) renewed every second year could be another option.
There’s only one answer, but people are a bit mixed up with visa and stay. When a visa is issued it always gives you a frame to enter and get your approved stay. That’s the validity of your visa and the length of stay is specified. As an example a tourist visa is valid for three months and gives you a 60 days stay at any day within these three months.
That’s not correct. A single entry tourist visa gives you a 60 days stay within 90 days. A multiple entries tourist visa gives you several 60 days stay within 180 days. The validity of the visa itself always starts when it’s issued.
But your permitted STAY starts upon ENTRY, so in other words you get the permitted stay at any day within the validation of your visa, also the very last.
Formally it’s 90 consecutive days and until day number 90 have come to an end, you still haven’t stayed for 90 complete consecutive days so you can just leave.
If you want to do a report anyway you can do it online between 15 and 7 days before due time and manually 15 days before due time.
First 90 days report after re-entering Thailand you’ll need to do in person. After you can do it electronically. Ask your immigration regarding update of your TM.30 each time you re-enter. Some demand update, some don’t require it as long as it to the same address.