The Thai consulate in Ho Chi Min City was issuing multiple entry non-o visa is married to a Thai before covid 19. Not sure about now since I have seen no reports of them being issued.
Requirements here: https://hochiminh.thaiembassy.org/en/publicservice/non-immigrant-o-accompanying-thai-spouse-and-family-members?page=5d80ab3315e39c2fe800a791
I am not aware of of what is needed to enter Vietnam.
Check this post in a topic on the Vietnam forum, https://aseannow.com/topic/1220017-vietnam-visa-update-big-changes/?do=findComment&comment=17306863