The dha is the indiginous sword of Burma and Thailand, sometimes called the Darb by the Thais. Almost all the weapon based arts from these lands and some parts of Cambodia, Laos and Vietnam use this weapon, but they call both the weapon and the arts different names. My guess is that "Dha Do" is just an attempt to insert the dha into the Japanese nomenclature, using the Do as a "way of" and insert any weapon before; voila, instant weapon art. The most common arts in the west that include the dha are Bando and Krabi Krabong. Consequently, the dha is not a weapon that is very well suited for use in an Kendo-like art. The blade is designed for hacking motions and not the sturdiest of weapons. Most of the targets that it was used against had less armor than what I would think is common in the times and areas where a katana was used.