Arrive with your Non-O, get a TM30 from your landlord/hotel, get a Thai sim registered against your passport, get a certificate of residence from Immigration using your TM30 then use these along with your passport and Non-O to open a bank account. Ideally do this in the first week or 10 days to enable you to transfer the 800k which needs to "season" for 2 months prior to applying for your 12 month extension at Immigration in the province where your latest TM30 is filed.
You are not talking about a Non-O retirement visa (which is 90 days) but the subsequent 12 month extension of stay which many incorrectly refer to as the retirement visa