I love the food in Thailand. One of the reasons I went back 3 years later.
Cooking class at the restaurant “Taste of Heaven”
Koh Phangan: One part is very touristic (Haad Rin, full moon party) and the other part is very relaxed (great for yoga).
Railay Beach (close to Krabi). I do not suggest to go there if you are a solo traveller. It’s a very beautiful island for couples. So one might feel in the wrong place.
Places friends recommended to me but I did not go yet: Pai (north) and Koh tao (great places to learn how to dive)