Heading to Mae Sot in the morning, I married my Thai gal last December and now heading to update my visa. I am applying for a Non-O marriage visa, is there anything that I might want to know be I leave.

You cannot apply for a visa ta Mae Sot there is no Thai embassy or consulate there.

Or are you writing about getting a new 90 day entry from a visa you already have. You can do a border crossing there to get it when you re-enter the country.

You can only cross the Mae Sot border if you have a valid re-entry permit or multi-entry visa already. No onward travel into Myanmar either.

9 minutes ago, Jdietz said:

No onward travel into Myanmar either.

That is no exactly correct. You can travel into Myanmar from there of you have a visa for Myanmar. A e-visa for Myanmar can also be used there.