Ao Phai is a beach about 1.5km south of Hat Sai Kaew along the island's east coast, quieter than Diamond Beach and popular with travellers who want a beach bar but not a crowd. The sand is slightly narrower and the water a little deeper, which suits swimmers more than paddlers. There's a good small selection of guesthouses and beach bars operating here, enough to make it a base for several nights without feeling isolated.
The beach at Ao Hin Khok, immediately north of Ao Phai, is worth combining in a morning walk: a statue of the mermaid from Sunthorn Phu's epic poem Phra Aphai Mani — in which the hero is stranded on an island strikingly like Ko Samet — stands at its northern end.