I stumbled across these videos from an American travelling linguist teaching Vietnamese by chance.
His insights are great and his Vietnamese is about 90% near fluent. Sometimes I really envy the linguists because I know how well they can explain the differences between 2 languages.
Check them out if you want a few tips, though I’m not putting him into my recommended resource list because it’s only 90% Vietnamese.
I’m not nitpicking, but you really need 10o% native Vietnamese instruction, especially if Vietnamese is your first tonal language.
I’ll try to upload my own videos soon, but until then…!