A couple years ago, I applied a Non O-A visa for my husband from outside Thailand which was a mistake. When almost his visa expired, we went to the immigrations, but he couldn't extend another year because we couldn't afford the health insurances' signatures to certify for the coverage. However, the officer told us there's a way by flying (only fly not cross border/not visa run) out of Thailand and flying back to Thailand again (we did flew out to Singapore and came back to Thailand same day). Then he got a 30 days stamp and after 15 days of stamp (or 15 days before that 30 days stamp expire). He must apply for a Non-O 90 days visa. Then wait until one month before visa 90 days expire, he must apply for a Non-O 1 year visa. I helped him to do and everything just fine like the officer recommend. I thought your mother should be fine with the same situation as my husband. These are a little bit complicated but as long as it works. I thought you can ask the immigrations for sure but your mom must be over 50 yrs. (My husband is over 50 yrs.) The important thing this kind of Non-O i year visa must have 800,000 baht in bank account to show to them. But I'm not sure about Non-O on Non-B visa. Hope this info help.