The viewpoint sits on the hill road that climbs from Kata Noi towards Nai Harn, and its Thai name is often translated as the hill of the three beaches. From the railing you look down on Kata Noi, the closest and smallest bay, then on Kata with the small island of Koh Poo offshore, and in the distance on the long curve of Karon. It was once called Kata Viewpoint, and locals still often use that name.
Few stops on Phuket give so much for so little time. Plan 15 minutes rather than an hour: a gazebo gives shade, small shops just below sell drinks and snacks, and the car park is free. Go in the late afternoon for warmer light, or early in the morning for clearer skies and fewer people, then carry on south to Nai Harn and Promthep Cape.