I had a week on Koh Samui in December 2018 - apart from 3 days of rain i had a great time. I rented a car for 3 days - I got an amazing off peak rate at Saboey Resort - near the Big Buddha - which suited me as it was very peaceful. I enjoyed Fishermans Village and Market for dinner. I Drove all over the Island.
I had dinner in Chaweng on the Saturday night - it was a bit like Kuta in Bali - and went to the most popular bar which is very low key and dull. Locals who knew each other and not friendly to visitors.
If you are looking for a great massage - had an amazing massage spa treatment at a gay friendly
www.emeraldgreensamui.com one of the best spa experiences I have ever had - totally legit.
Koh Samui is awesome for a laid back holiday but if you are looking for buzzy gay beaches and buzzy night life - not the place