As long you are Asian doesn’t matter which country you from or if you have Chinese blood or look like Chinese, Vietnamese people will think you are Vietnamese. Yes! You are.
Not majority I think but it depends if you have similar skin colour as Vietnamese or look like Vietnamese. I am often being mistaken as Vietnamese because my face looks like Chinese although I am quarter Chinese but I am not Vietnamese. This has caused me language barriers, as I do not understand what they are said. 3 months I have lived in Vietnam, very little words I know. Only limited to “How Much?” “Thank you” “Hello” “1, 2, 3, etc”. Only these words surely enough to let the local people knew that I am “I know your words/culture so do not try to cheat me”.
It is crucial to learn even just a few words. Also I have downloaded an app that can teach me Vietnamese words. It’s called “Vietnamese” and the logo look like a bird. So far, this is the best app compare to others. Every time went out with foreigner friends; Vietnamese will look at me and talked to me like I understand every word that they are saying. This kind of situation never fails to happen every single time.
As you all know, Vietnam is a hot country but also the sky loved to gives rain. Even in this hot and sunny weather, Vietnamese still able to keep fair and white skin color. Compare to other Asian country such as Malaysia I would say less hot than Vietnam because even after walked after 10 minutes you still will not sweat (unless running/jog), but in Vietnam even before I step outside the door, I already sweating so much.