Yes, Chatuchak market has a pet section. Maybe not somewhere a tourist is going to make their next purchase, but certainly worth checking out. It is home to many breeds of cats and dogs and the list truly does go on.
There are pet accessories including leashes, cages and toys, tanks and soaps for aquatic creatures as well as foods for different types of animals.
If you're an animal lover and fall for a pet from the market, make sure you do as much research as possible before making a purchase. It is often very difficult to get these animals through customs when travelling home and can be a very costly exercise.