My three month Non-B expires in a few weeks and I can't extend it for contractual/medical reasons. It would be convenient to stay for another month though.

Is leaving the country to return on a visa exemption an option, perhaps a risky one? Or leaving and applying for a 90 day tourist visa or even a transit visa at an embassy or consulate abroad, maybe just as problematic?

I have assumed that there isn't any option at local immigration. I have gone from tourist to Non-B at local immigration but haven't heard of anyone doing it the other way.

I had intended returning to Europe for two months, it would be easier to recover from my recent operation, but perhaps an extension of stay would prejudice any attempt to return in April or May. 

Any help much appreciated.

You can leave the country and then get a 30 day visa exempt entry without a problem.

If you leave the country at a border crossing and come back in, you'll get 30 days Visa exempt,and you can extend it another 30 days at your local immigration office. 

Ubon Joe is correct

Thanks for the info. I will probably take that option and then travel home to return in May as, apparently, I will be able to come back from Europe on another visa exemption at that time. I take it that I can leave and return next week by either air or land.

Thanks again.