Mystery solved! This sword is likely to have originated in northern Thailand or Laos. It is a relatively rare and oddly shaped dha with a complex recurved back. This style of blade is also found on pole arms from the region. It has been positively identified by an expert in that region.
This is an unknown sword which previously identified as a parang beng kok from Bali, 19th C. It is a very rare sword, and it remains somewhat of a mystery. "Beng kok" simply means "bent".
It is here in the Cambodia section since my recent discussions with other collectors lean towards a Cambodia/Laos/Vietnam origin.
The sword was in the collection of Anthony C. Terri and and published in his "Islamic Weapons" book as figure 300B on page 424. Earlier, Van Zonneveld (page 98) and Gardner (plate 58) also identified as such. However, even with such an awesome pedigree, there are those in the community of collectors who doubt this identification, and they are not wrong to do so. All published works on ethnographic edged weapons inevitably contain some errors. In this instance, it is quite possible Gardner made the first mistake and the others merely repeated it, with or without citation.