Currently there are 22 native Standard Zoom lenses for Pentax K-S2 and all of these lenses are autofocus (AF) type.
K-S2 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on K-S2.
Since Pentax K-S2 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 7 Standard Zoom lenses with Weather Sealings.