Don't forget that the day you arrive is day 1 so a 60 day entry gives you 59 nights stay and your airline may require you to have proof of onward travel within 60 days of arrival, check with them
Therre is no seasoning for your 800k for your initial Non-O (except in Jomtien) so no border bounce necessary as long as you can open a bank account in time
Technically you do not need a Thai bank account for Retirement Visa and subsequent Extensions of Stay as long as your Embassy still provides the income affidavit.