Wow, so many questions. I knew people would be saying "I lived there for years and no one stopped me." Don't know what to say other than this happend to us. The first time I was stopped it felt like they really wanted to know if I was overstaying but I find it unsettling for them to just randomly just stop me without reason but I guess I play by their rules. They asked me a bunch of questions about when I got there, when I was leaving etc. which they wanted to match with my passport. My partner does not allow me to carry my passport. Affraid I will lose it. Now I am white and he is Asian. Maybe that seems "odd" to them.
The 2nd time they concentrated on my partner. The "dozen" agents converged BECAUSE the first agent could not speak English and they were confused why my partner could not speak Japanese. What was freaky about the agents is they were normal looking people in regular clothes standing around the subway pay station during rush hour and they came out of the blue both male and female showing us their badges. The country must be crawling with undercover people. They did say it was "mistaken identity" but it seemed like a lie to me. We were arguing as we bought the subway tickets so maybe the thought the "Asian" was trying to scam me. There was also an incident many years ago of some people gasing and killing other passengers on the subway so maybe they are on high alert from "evil" Americans.
However, anyway you look at it is very unsettling considering I have been to Vietnam so many times over the past 15 years and have never even got a look.