If you can make contact with an aptly-named Irishwoman called Christina Noble who runs a children's home in Saigon (sorry, Ho Chi Minh City), she may be able to point you in the right direction because she also sings and plays guitar. I don't know how involved she is in any music "scenes" (especially as far away as Hanoi) but she's lived in Nam for years and is probably pretty aware of whatever's going on.

There's a book about her called "Mama Tina" which gives more info. Good luck in your interesting-sounding work, and let us know how you get on!