you are confusing what people call a retirement visa (Non-O-A) gotten outside the country at the thai consulate in your country before you wing your way here (which requires the background check and the medical certificate with getting a 90 day Non-O visa and then the yearly extension inside the country at the immigration office
@David *********
, gave you a pretty spot on list of requirements. I'd say to go the Jomtien immigration office and get the hand out they have listing the requirements.
You need to apply for the 90 day Non-O when you have at least 15 days left on your current stamp because it goes under consideration for 14 days before you go back and get the new Non-O visa and 90 day stamp inked into your passport.