What is the procedure to change from Visa Waiver to Non-O Retirement Visa and how do I request a 12-month extension before my 90 days expires?

Do t forget the financial requirements

You aren't "changing the status" to anything, you're not here on any visa, you're here free stamp entry, you would be applying for an in country 90 day Non-O visa for 2000baht using form TM87 application for visa

Go out to Chaengwattana get the hand out listing the requirements for the in country Non-O visa from Section C-1

get the documents, copies, bank letter, lease, TM30, land lord i/d house book etc together

Go apply when you have a minimum of 15 days left on your current 60 day visa exempt, pay the 2000baht, get a receipt that says to come back in 2 weeks, on that date go back to Section C-1 and get the Non-O visa and a new 90 day stamp inked in

THEN you wait until you have 45 days or less left on the 90 day stamp you got and go back to Chaengwattana with all new documentation and apply for a year extension of stay in Section L-1 for 1900baht. It will be issued on the spot and you get the passport with the year extension in it

Make an appointment is fine, for Section C-1 to apply for the visa, and then when you go to apply for the year extension in Section L-1