I immediately thought of your iron-handled dha, JT. I think I have seen one other that has that same tapering handle. I'm thinking the first one of Charles' is from Burma, especially since John's has a concave tip. I was just looking that the pictures on John's web-site, and am I right that it has some nice activity in the blade?
The fullering on your (Charles's) is pretty distinctive, I think. Two small fullers and one larger one. I have seen this on a few other dha, and now I want to go back and compare them all to see if there are other similarities.
I'm a bit undecided about the second one. I see where Andrew is coming from in attributing it to the Rattanakosin era. I have one that I am reasonably sure is Rattanakosin era Thai, which has a lot of similarities to it (blade shape, obviously, handle/blade proportion, the facetted ferrule).

Another Rattanakosin daab I have is similar in the design on the facetted ferrule:

But there are differences from both of these, namely the larger lotus pommel and braided rattan grip on Charles'. Those look more Northern Tai or Shan.
But, I also have seen very similar pommel designs on Burman dha:

But here is another one which I am fairly sure is Thai:
I lean away from a Kachin origin for the second one mainly because the handle is too long. Some Kachin groups apparently do use a Shan style handle (with the lotus pommel and facetted ferrule) on a short, square-tipped blade like this, but the handles in photographs I've seen are shorter relative to the blade than this one seems to be.
Here is the final plot twist (this one I am very sure is Shan or Northern Tai):

We used to think this was Kachin, but I have now seen several old photos of Shan warriors with dha-lwe and dha-hmyaung with this identical scabbard design, which has convinced me that it is a Shan style (plus the maker's mark on the blade is apparently a Tai mark).
So, I'm going with Shan, but from over the border in Northern Thailand. It sort of accounts for all the various elements - sort of Burman, sort of Kachin, sort of Thai/Rattanakosin. Of course, in a couple months something or someone will come along and show I am completely wrong.