If you’re visiting a Vietnamese person’s house, when you leave you must tell you host this. Even if it’s obvious, it’s necessary to actually say “I’m leaving” – especially to those older than you.
Usually this is with the verb “về” (as in, I’m going home). For example:
Chị, em về.
Chú, con về.
But there are times when đi (to go) is used, for example if you’re heading to the bus station to leave town.
Bà, con đi.
Anh chị, em đi.
In my experience, Vietnamese people love it when you follow this custom. Next time you’re visiting someone’s house or leaving a party, try it and see.