The way it works in Bangkok
@Scot ******
to apply for an in country Non-Immigrant Type visa IS
You need a minimum of 15 days left on your current stamp (to cover the under consideration period the application goes under)
You go to Chaengwattana Section C-1, you apply for the 90 day Non-Imm visa, pay the 2000baht, get stamped on the receipt when to come back. On that date you show up, go back to Section C-1, give them your passport and the receipt and they will ink the 90 day Non-Imm visa into your passport stamp it used and then give you a new 90 day stamp dated from the date you applied for the visa (14 days ago) You will lose any time you have on your current stamp.
Then when you have 45 days or less left on the NEW 90 day stamp you go and apply for a year extension based on what ever reason you're applying for (retirement marriage to thai, etc)