Yes they do trade buckets for dogs, although I have noticed that not all the Thais up in Isaan eat dog meat. In fact, very few of them do, and those who trade in the dogs usually only trade them in if they become a nuisance.
BTW.....dogs will often refuse to eat commercial dog food if they've never had it before, but I don't think they'll refuse to eat it to the point where they die from starvation. I know many many people who keep dogs think they're doing the right thing by feeding their dogs "human" food, but the truth is, commercial dog food is actually better, unless you really go out of your way to prepare a properly balanced diet for your dog. I've always fed my dogs commercial food, and have to date never had a problem.
As you say, most of those dogs that died probably had underlying health problems.

Don't try to impress me with your manner of dress cos a monkey himself is a monkey no less - cold fact