I also enjoyed cycling around Koh Yao Noi, especially through the rice fields. Apart from two big climbs, it's quite easy. Otherwise, there are also diving excursions leaving from here, kayaking, yoga, even rock climbing, and a few spas and massage parlors.
For those who would like to make the most of it, I can recommend an all-inclusive package to discover Koh Yao Noi with a guide. It will introduce you to koh Yao Noï local life, the superb bay of Phang Nga, and the interior of the island for 3 days (see below).