Native of Thar here. Not from a farming family but it is extremely likely that this is for farming. Land tend to be arid and barren so selected passages that are low lying are cultivated just before monsoon season in the hope that water logging in the monsoon will irrigate it to get some crop.

I also translated the only book about the culture of Thari people from that region. Pdf link for anyone interested: https://github.com/ketancmaheshwari/dhati-book/raw/master/ma...

Yes, and it looks like a "space filling" pattern with enough room between to do something like farming. It does not look like an abstract artwork.