Hi Surbhi! Yes, direct buses from Mahabalipuram to Pondicherry are available and in plenty.You will have a lot of options as buses ply every few hours. Most of these buses will pass through Chennai. Some might require you to change buses in Chennai (Thiruvanmiyur or Sholinganallur) but it is barely a 2 min change. You can also contact bus booking agencies for assured seats and bookings. Happy Travelling!