Hmmm I'm going to be visiting family in Vietnam next summer. I'll be sure to ask around. Its called NamBlack?
That would be awesome, I believe it is a landrace that was found and used by the occupying US soldiers while policing the country.
The buds when dried are as close to black as one can get.
There are other strains in Vietnam that are more readily available but, this Namblack should be well known by those who live there.
I hope you are successful in finding some, if you do I sure would like to hear about it
Have a safe trip !