Yeah, Chiang Mai is pretty nice. Lots of temples to visit and the like but it came alive at night for me. Keep out of the main town and just head round the market squares near where you’re staying. Loads of local pop-up bars & food places. Best Tom Yum Soup I had during 5 weeks in Thailand was cooked on a camping stove round the back of a local grocer stall in a marketplace carpark south of the main city.
For Koh Samui, the north end was really touristy when we were there. We hired a scooter and went exploring. This place is beautiful and does an evil papaya salad. When the owner stopped laughing at us she let us run down to her garden to pick bananas to get rid of the heat.
We also hired a boat somewhere near to here and went sea fishing then sunbathing on Ko Mat Sum island.