There are quite a few excursions on Chang Island. A sightseeing tour of Chang usually includes an elephant ride. The cost is around 650 THB and up. There are no bus tours on Chang, they just don't make much sense. There is one central road, going almost to the southern tip of the island. But minibuses can take you anywhere you want to go.
The cost of excursions in Chang starts from 500 THB, depending on the itinerary. For example, guided jungle hikes cost around 800 THB. Among popular Russian excursions and tourist projects on Chang Island are boat trips around the island, diving training, sightseeing tours. The cost of such delights starts from 1000 THB.