I don't know what will happen in the future. I always take my annual pension statement to immigration at each annual extension, but it's never been requested. With the shonky bank business going on in Thailand at this time, it wouldn't surprise me in the least if source of funds is required in the future. That'd be great, as I'd be watching those with agency accounts squirming as they try to explain the sudden appearance of 800k in their accounts!
Thad's correct. It's getting more difficult to convert in-country from visa exempt to non-O. I fully expect this avenue will be stopped in the next year or so
Yes you can. You can obtain a non-O 90-day visa from an immigration office, which then cancels your 60-day visa exempt entry. There is no requirement to leave the country