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 'เพื่ภ[for/for the purpose of] retirement' stamped on it, so maybe that makes it different circumstances from the marriage version, dunno.