My WP cancelled 1600 one day (and thus the non imm B). Next day went for non imm O- had all documents ready. 2 days overstay!

Beware, my WP was cancelled and I got receipt too late to go to imm that day to change from B to O. Got there at 0900 and had all the right stuff but still got charged 2 days overstay. Go figure!

Can you afford to lose it?

That's it.

I have done(Jomtien)the annual extension of non imm O based on retirement for a number of years. Never done a med certificate.

A non imm B visa is not an authority to work per se. It is required before a work permit(wp) can be issued by your provincial labour office. An alternative to the B is a Non Imm O based on marriage to a Thai national. I worked on a WP for 9 years and never left - I extended annually at immigration. Having had a 5 year gap I am doing it all again.

Don't. You'll never get back what they will thieve from you sooner or later.

Thanks, as long as they don't give me that Thai attitude that some in 'authority" are well known for!

sounds good.

Would Cambodia be an option?