I'm not an expert but the scabbard and tsuba combinations are similar to the ones listed as Cambodian on Mark's website ( they're actually are part of Ian's collection ) . There's a picture of one of them on the History of Steel's website:
http://www.arscives.com/historysteel/images1/263-iag04.jpg
The turned wooden grip looks Thai ( Siamese ) and many modern Thai daab share this feature . The knife looks like a Thai priest knife and I would agree that the markings look Thai .
I think Ian's subsequent response would give you the definitive answer to your questions.