The opening of the account happens immediately. You leave with a bank book, ATM card and Swift details for foreign transfers. I opened mine in the K Bank in the subway under the Interchange 21 building between soi 21 (Asok Montri Rd) and soi 23.
O based on retirement 800k in the bank or 65k per month income. Based on marriage 400k in the bank or 40k per month income plus photos together at the house, and other widely varying proof you are in a genuine relationship. Some people find the proof part quite tiresome.
This is not actually correct. If you convert from O based on marriage to O based on retirement there is no need for health insurance. Only conversion from O-A requires health insurance.
Yes, go on an O based on marriage and then get 12 month extension if you deposit 400,000 baht in bank for 2 months prior to expiry of the O visa. No problem.