Many boat tours stop by Koh Ta Kiev Island for an hour or two as part of a 3 island trip.

You can also leave in the morning from Otres Beach and come back in the afternoon.

The trip from Otres is typically 55 minutes each way.

The 3 island trips cost $15 including lunch. 

You can rent a boat to take you to the island for about $50 one way, and get up to 20 people on the boat.