@Anthonie ******
as I said extension are added on to the date of your current stamp expiration,
SO
if you're on an entry stamp from a Non-O visa that expires on the 19th of May & you meet the proof of funds etc, now, you can apply for the year extension any time after the 19th of this month.
The extension is 1900baht and once you get that you tell them you want a re-entry permit and that's 1000baht for a single re-entry (where you can exit/re-enter once) or 3800baht for a multiple re-entry (where you can exit/re-enter all you want the coming year your extension is valid for)