@Mario ********
as you are still in the first year of the OA visa...
IF you LEAVE THAILAND and return to Thailand you will be stamped in for One additional year.
All that you need to get it is the OA Insurance policy for another year.
A border run to Laos, Cambodia or Malaysia will get you the re-entry needed to get the Extra year extension of the OA visa.
During the second year...if you wish to leave Thailand and return... you will need a re-entry permit... cost of 1,000 Thai baht per re-entry permit.