Avoid having to leave country, just get non O based on retirement before you arrive. Deposit the 800,000 tb in advance. . Then do the 12 month extension for 1900tb. Plus buy a re-entry permit so you can go back and forth on trips.
things have changed and the days of entering on tourist visa and opening bank accounts has become almost impossible, I guess you didn't realise. Most banks now want to see long term visa like Non O. Shame you didn't get that before arriving.