not if he does the financial proof for the Retirement extension by the affidavit of income from his embassy. As he apparently is a German citizen, he can use the affidavit
so you better got a printed copy in backhand when you visit your Immigration, to be prepared if they tell you that the Q-Code on your mobile phone is not sufficient
if it is "that bad" or not - that's not YOU who decides it, but a doctor or a hospital. If you conceal pre-existing conditions, every health insurance can kick you from the contract
the 90-days Non-Imm-O is regarded as a longterm visa, so a bank will normally be willing to open a bank account for you. Of course if you meet incompetent bank staff, and it's lots of them out there, who will pull out of their noses fantasy stories to prevent telling you that they have no idea (face value loss) so you might feel that you are better off using an agent service. Actually a 90-days Non-Imm-O visa, a certificate of residency from Immigration and a Thai mobile number is all you need to get a bank account opened
the 90-days Non-Imm-O is regarded as a longtermn visa, so a bank will be willing to open a bank account for you. Of course if you meet incompetent bank staff, you are better off using an agent service
you forgot to mention that after been issued the 12-months extension, there must remain a minimum of 800,000 THB in your bank account for at least three more months
I can always buy another single re-entry at the airport or a land border or on Immigration. A multi re-entry permit costs 3800 THB. So even if you plan three exits and re-entries during the 1-year period, buying three separate single re-entry permits is still cheaper