@Scott *****
you can NEVER EVER renew a visa or an extension of stay.
Be that as it may, IF you get that O-A visa from the thai consulate in your country before you come here you will have almost 2 years of stay in country before you need to apply for an extension of stay.
So while it'd be a good while down the road before you need to apply for a yearly extension; you'd need to bank 800K baht in an account in your name only for 60 days before you applied for your yearly extension of stay.