My girlfriend has a non-immigrant B visa for purposes of visiting a local branch of her company for meetings throughout the year. Unfortunately, she wasn't able to get multiple entries, so this visa is only good for current business over the next couple months and then she isn't covered later in the year when she will have to return.

She is Korean so actually being in the country isn't a problem (issued 90 days on arrival), but since she will be working during these times, she wants to be issued a visa in compliance. She isn't employed through the Thai branch and is therefore ineligible for a work permit.

Anyway, my question is: can she extend a single entry to a multiple one or have a re-entry permit issued and extend the period covered from the original 90 days? If she got a re-entry permit before the end of 90 days, could she come back in for another 90 days or just the remainder of the original?

I'm not sure I understand this situation perfectly, but this seems to be the gist of it. Any help would be appreciated.

Working without a work permit is illegal. You say she is working illegal already on her non-B visa, so what would be the diffrence on retuning on a 90 day visa on arrival?

She can't extend her non-B other than only by 7 days if she can show a ticket out of the country within those 7 days. Seems she will need to get a new non-B visa. A re-entry permit only keeps the original permission to stay alive, it doesn't give any extra days.