strictly spoken, the Non-O/A visa is NOT the "retirement visa". It is called "longstay visa". The only "real" retirement visa is the 90-days Non-O visa and the subsequent 1-year Extension of the Stay Permit based on retirement. Most people call the "extended stay perm it" a "retirement visa", which is WRONG because a stay permit is not a visa
as soon as your theoretically 2 years out of a Non-O/A visa are over, Immigration will require a Thai private tgia-listed Health Insurance. Your Allianz Global will not get accepted by Thai Immigration
while you can get another full year admitted stay on a Non-O/A visa if you enter before the visa itself expires, the period you get stamped in depends on the validity of your health insurance which you have to present the Immigration officer at the border. You won't get stamped in for any longer than the validity of your health insurance. During the "second year" of a Non-Imm-O/A visa, you have no more re-entry permit. In case you plan on leaving and re-entering Thailand, you need to buy a re-entry permit