Anyone who has lived in NE Thailand or Indochina for long is aware of the dog trade. I certainly am. It's just one of those disagreeable parts of the culture that is widely accepted but not appreciated by most foreigners.
If you have a dog you keep it close and as with all things when eating at restaurants with friends it's best to know what you are getting into. Besides dog, restaurants also sell wild bush meat which might be harmless or might be an endangered species, best to stick to pork, chicken, or water buffalo.
I've read articles before which gave pretty accurate descriptions of the trade. I even made a post about the issue which I'm too lazy to look up and link to. The long in depth article in Friday's Guardian was better researched and written than any I've seen on the subject yet.
The writer follows the route for dogs from Thailand across Laos to the Lak Sao border which I've also written about in relation to the very large illegal trade in logs. Eventually and disturbingly the writer ends up back in Thailand, with his narrative if not his travels, and visits the holding pens for the dogs rescued from export.
Thailand like other Theravada Buddhist countries can't abide killing things. So they keep thousands of confiscated dogs in small cages until they die of overcrowding, malnutrition, fighting, and disease.
I think human beings can do better. We must face the reality that unwanted or animals impossible to care for exist, and that if we are their caretakers we owe them as quick and painless a death as possible.