Am not trying to start a Vietnamese bashing here.
Yesterday, someone needed my apartment for a meeting. A teenager was accompanied by his father. Both felt it perfectly normal to i. open doors and ii. then they disappeared into my bedroom. Minutes later, they re-appeared.
They knew there was a second toilet.
To me, that's very rude behavior. Like grabbing a lady's purse and going through it to see what junk she is carrying around. Condoms? Meds? Cigarettes? ...
At the time, I had 6 million Dong cash lying in there and feared they might steal it. But that was not the case. What were they doing in there? And: Is this "common", "normal" behavior?
I also committed a faux pas by asking for "say sauce" - they didn't have any!