I need some money short term for major medical. Any chance a bank will loan or give a credit card with a retirement visa? I can show good monthly income deposited to BKB every month.

Virtually impossible, unless you can put up collateral or have a credit worthy Thai person to sign as a warrantor.

As a foreigner you could leave at any time - expect you might have more luck with the medical facility providing payment options or use a government facility at much lower cost than most private hospitals (often an option).