Hi Freddy,
I'd posit the Annamite mountain chain as a possible place of origin (Vietnam, Cambodia, Laos).
I heard that a similar blade was used by the Mnong minority in the southern part of the mountain range but didn't managed to see a piece first-hand. I got this information from a western aid worker in Vietnam; a drawing shows a slightly more elongated blade with the edge on the outside curve but this may be an error. There are a lot of different peoples (some with widely divergent origins) scattered across these mountains and I've no idea which ethnic groups may have used similar blades; the Mnong are usually placed in the mountain Khmer group though which would point to a southern origin.
I'd assume that these once doubled as tools/weapons like many agricultural implements. I don't think the leather is original - much more likely to have been braided rattan or other plant fibers.
BTW, if you later on decide to toss it, please make sure to send me a note!
Regards,
Kai