Surfing in Tonga is limited to a few good reef breaks for advanced surfers only and located on the western tip of Tongatapu at Ha'atafu Beach. with a couple of more isolated breaks in the lagoon including around Eua'iki. There are no beach surfing in Tonga for beginners or body surfing beaches.
At Ha'atafu Beach there are three or four reliable lefts during the peak Winter months (May to October) produced by the southern swells from New Zealand and beyond. From November to April the north swells that peak in Hawaii also reach Tonga but with less intensity and these produce some good rights at Haatafu. These breaks are accessible from the beach and less than a five minute paddle away. There are also a couple of passage breaks along the fringing reef which are accessible by boat. There are seldom more than a handful of surfers at any of the breaks, even the ones with direct beach access, so you're going to have a lot of surfing with no local bragging rights going down.