Slim chance getting a US Embassy to certify your docs. They quit certifying docs that the don't have direct access to (like, they can't log into the database and verify it) some time ago.
I'm new around here (this forum, not Thailand), so you haven't heard me myself telling you this before but you will now. I just paged back through my passport and I definitely have a 'non-immigrant visa' stamp, category 'o', with 90 days of validity stamped on it. Which (trigger warning pendants!) I will call a 90 day Non-o visa.
It's from 3 years/extensions ago so maybe things have changed in the interim, but I definitely got it inside the country i.e. *not* a border run. It also has 'เพื่อ [for/for the purpose of] retirement' stamped on it, so maybe that makes it different circumstances from the marriage version, dunno.