Is it actually stranger or just a strange person? They're two different things in English.
Stranger. As in, neither friend nor acquaintance.
Oh so literally just strange person in Vietnamese? Neat!
For a strange (weird) person, it should be "người có tính cách lạ" (lit. person that has strange character)
Additionally, to indicate a strange person, a "stronger" adjective is needed, e.g. "người kì lạ" (not "người lạ").