What options does my mom have to extend her stay in Thailand after her tourist visa?

@Bonny *********

, If she can meet the financial requirement for Non-O being over 50 or Non-OA, I recommend getting one of those.

Or see how the traveling around neighboring countries when she makes her trip a few months later, maybe METV could be one of the choices.

Seeing you are expecting a newborn baby, I'm not so keen to recommend it to you while as Benjamin says Non-O dependant to Non-B holder is one of the good options if your employer agrees.

WIth Non-O dependant to you, that means you have to be next to her at the immigration office when she applies for a visa/extension because you are the reason for her visa/extension. YOU, no other family member, have to be there, and doesn't matter you are in labor or your newborn baby is sick.

Or if you happened to quit your job, her extension is invalid with yours. (while you have a choice to be on Non-O marriage, she may not have many options)

You may want to consider these parts, too.