IF you qualify, then definitely apply for the LTR visa. Gives you 5 years, with 5 years extension if you still qualify and several benefits (tax, etc..)
If not, then "retirement" visa, yearly extensions.
If based on marriage (yearly extensions), there is a lower "money tied up in the bank" requirement, but more hassle with the paperwork.
you deal with visas every day, but youndon't know the difference between the actual visa from Thailand - which what you get BEFORE you pass the immigration booths, and the entry stamp/ permission to stay stamp is which you get when the IO officer in that booth stamps you in ?
OP didn't have a visa, OP was visa exempt. So OP didn't get a visa when he got stamped in either. He git a stamp which allows his stay, which is not a visa.
Visas on arrival have to be paid for, and are obtained BEFORE you pass the immigration booths.