If you want to extend for one year from an O-A you also need a health insurance from a Thai insurance company. You don't need this if you extend from visa except or TR.
You can find it at many websites already, but as Benjamin said... it's not official yet. There was just today another story from a guy from the U.S., his CoE was refused because he booked "short" ASQ already; his arrival was planned in April. Also... the list with the eligible countries isn't released yet. So... everything is still a big "maybe" right now...