They might use them in Borneo but the first thing that comes to mind is a Kris, a style out of the Indonesia area, Bali, Philippines,
the name kris seems to be used over a range of blade forms, straight and wavy, mostly equal thickness to highly tapered , the waves plus the curved handle definitely puts in that part of the world but I don't think the shape is distinctive enough to place it in one country unless the engraving means something