Whichever way you do it, carry 20,000 baht/equivalent in cash with you. With 8 months stay you might get pulled for a check. It mostly never happens but better to be prepared.
Yes. You do not need to enter before the 'stamp' runs out. When you enter after it runs out you get a new 'stamp' for another 60 days which can be further extended for 30 days at immigration inside the Kingdom.