Yes, I agree Ian, great to see Mark posting again
Trenchwarfare, thanks for sharing. Vietnam war bring backs are interesting...if accurate you would think that this would be from among the different Tai groups that live in Vietnam and Laos. It's a basic working blade that every man/ household would have as multi-purpose jungle/ bush knife/ tool. That being said...I've also seen similar from Thailand and Burma as well. Mark mentioned Shan...which reminds me of a knife from the Shan states I've seen before with the same type belt loop binding as this one...and it did have a carved/ gouged grip handle as well...but I'm not sure if this would be enough for it to be exclusive to this region.
Here are some more recent working blades I picked up...which at the time I perhaps perhaps mislabled as Karen...it was actually a temporary village set up of sellers from various ethnic groups...the blade shape I know now is considered Hmong style...and could be obviously carried by a non Hmong person...nowadays at markets you see usually just the knife or sometime just the bare blade...and the buyer then has a handle put on and scabbard made
http://www.vikingsword.com/vb/showthread.php?t=5163