Almost at the northernmost point of Pulau Aur. If you are not too sure, Teluk Ba'ai is the beach fronting the Atlantis Bay Resort. Distances from Batu Kembar and Teluk Berhala are 5 minutes and 1/2 hour walking, respectively.
Teluk Ba'ai can be described as a secluded bay on the far northern end of Pulau Aur. It is quite close to the mouth of the ocean channel where it meets the South China Sea. Don't worry though, the beach is sheltered enough from the frequent strong breeze predominantly seen on sections of the island that face the wide open sea.
The beach area is considered very small by any standard, but by no means it is less beautiful. The waters are just as crystal-clear as those seen in Batu Kembar or Pasir Putih. Nonetheless, the beach is quite rocky at parts, so do thread with caution.
There are probably not much activities can be done here. I observed only one or two beach chairs provided by Atlantis Bay Resort due to space constraint. Since the water is very shallow and there is no boat jetty at the beach, oncoming big boats will have to dock somewhere in the distance, from which the passengers or divers will have to transfer into a smaller boat to get to the beach and the resort.
If you get the chance, make yourself to the well-marked walking platforms on the left side of the beach. It will bring you a few metres above the ground, from which spectacular view of the bay and the sea channel separating Pulau Aur and Pulau Dayang can be soaked up.
Overall, quite a great beach although the activities can be very limited here.