Bill:
Interesting that you should have been told your example came from Luzon because that is one of the last places I would expect it to have come from.
Almost everything about this knife says "not Filipino" to me. First, the blade shape is not traditional for any of the local groups in the northern, central, or southern Philippines. Second, the tang arises asymmetrically from the blade, being located near the spine, rather than centrally. Third, the hilt is unlike any that I have seen from the Philippines, and it is blind tang construction (very unusual for knives from Luzon). And lastly, the wooden sheath is much lighter in construction than the vast majority of Philippines pieces I have seen, with just a thin single rattan strip to hold it together -- not the usual sturdy Filipino construction.
It may have been collected in the Philippines but I don't think it was made there. What I have found with many Filipino attributions, especially post WWII, is that the sources are often ex-servicemen who were stationed in the Philippines (and elsewhere), and often traded with other servicemen who had traveled in the region. Can't remember how many recently made Thai dha I have seen that were said to have been brought back from the Philippines. Also, we had a long discussion a couple of years ago about Taiwanese knives and swords that turned up in the Philippines, and whether these were indigenous to parts of the Philippines (probably not).
One other thing I did not mention above.
There are lines and "X"-es marked on the spine of the blade, just in front of the ferrule, that are discernible in the close up picture of the hilt. These are reminiscent of the marks on some 20th C. Thai dha.
Of the suggestions so far, Andrew's Thai knife seems to come closest in appearance.
Ian.