Hin Wong lies in a small sheltered bay on the east side of the island. The main features are several flat-topped rocks covered by a wide variety of corals. A steep sandy bottom slopes away from the boulders.
Aside from all the different corals, you'll also find a wide variety of fish here as well. There are blue-spotted and red coral groupers, which can be quite curious. I did one of my Open Water certification dives here, and had an audience of a couple of the guys. There are also bannerfish and Moorish idols. This is also supposed to be a good place to spot green and hawksbill turtles, although I didn't see any.
Although you can visit the site at any time, it's probably best from March to October, when the bay is sheltered from the southwest monsoon winds. The rest of the year, when the monsoon shifts to the northeast, the bay can be choppy.