@Wayne *********
works like this, IF you arrive on an O-A you'll get stamped in for a year (or as long as your health insurance is valid for). IF you arrive on the O/X you get stamped in for almost 5 years.
Your wife arriving on a single entry Non-O visa will get stamped in for 90 days. <- when she has about 30 days left on that stamp, you BOTH need to go to the immigration office and she will get a year extension based on being the spouse of someone on a "long stay" (retirement) visa for 1900baht.
Only THEN will she will start counting to do the 90 day reporting. You on the other hand will have your first 90 days report due 90 days from the date you stamped in.
You are correct if you get the O/A it is multiple entry and you can come and go all you want on that visa (the O/A will get you stamped in for a year every time you enter or as long as your health insurance is valid for)..