If we define folklore as the traditions, humor, and hardships of a culture or the people of a region, I think Their Eyes Were Watching God could certainly be considered a folk tale. The two primary instances are the town of Eatonville and the more migrant setting in Florida. In each, we learn the peculiarities and dialects and characters (all of which provide some humor) particular to that place. Think of the freedom to do and achieve which was given to the residents of Eatonville and how little they did with it due to their culture of always having being told what to do. In the migrant camps, playing dice and playing music, as well as all the unspoken politics of the class system among them, provide entertaining incidents and characters, as well. They are historic and real reflections--another reason this might be considered, at least in part, as a folk tale.
Are you talking about types, or themes, of folklore? It is kind of hard to answer this question when we don't quite know what your question is...
I'm not exactly sure what you mean by Folklore groups, per se, but folklore certainly plays an integral role in the novel. Zora Neale Hurston was a folklorist and spend a good deal of time traveling through the South documenting many of the folktales told in those times. We see many of the tales appear in one shape or form in the novel. For example, the story of Matt Bonner's yellow mule, the story of the Sinclair dinosaur, etc.
What I mean are the elements of folklore and their importance to the novel. Could this novel be considered a folk tale? How?
I don't really understand what you mean by groups either. Poster #2 had it correct that one can see in the novel different forms of folk tales concerning the dinosaur, the mule, and other incidents. There are actually quite a few, too many to list individually.