They are fishing boats that use high intensity lights to draw squid to the surface. Each boat can use more than 100 lamps.
The area you are talking about is just outside the exclusive economics zones of Oman, India and Pakistan and is a bit of a free for all (unregulated but not illegal).
Boats are there from September to May and stay out during this time.
You can read more here (relevant part starts from the 4th paragraph):
https://earthobservatory.nasa.gov/im...n-night-lights