If you can get to Koh Klang island in 10-15 minutes from Krabi Town by taking a longtail boat from the Chao Fah Pier which hosts a nice little night market every evening or the Giant Crab statue, I recommend you take a more complete boat tour which goes to Khao Kanab Nam, the two most famous rocks of Krabi river, their cave and its monkeys and the mangrove tunnel that at the end open on ... Ban Koh Klang ! The boat tour with visit to the highlights of the island generally takes half a day. You can also choose to stay there longer and even sleep there. There are several guesthouses or homestays like the Nisarine Hostel
See here a list of accommodations close to Ban Koh Klang Community
To go visit Ban Koh Klang Community, you can also book one of the tours above.