I fairly certain Vietnamese do. I know they used to during the Cold War.
As for the borders, Two months ago, just caught a Caucasian terrorist (Hezbollah - Lebanese) in Detroit who came through Nogales.
I think you are right about the Vietnamese. I'm not sure abour Laotians. Around here, they seem to be liberal oriented and to have acquired negative urban cultural attitudes.
The Vietnamese were genuine political refugees. The kind of immigration I am all for.