Your original 90 days was not an extension, that was the Non-O which allowed you to get your 12 month. Look at your 12 month stamp, it says "12 month Extension of Stay" not "12 month Visa". extension
It's still a 30 day extension which, in most offices, can be applied for when there is 30 days or less remaining on your 60 day entry stamp (Jomtien & Pattaya is 7 days or less remaining)