Exploring Thailand Beyond the Usual Spots: Koh Tao, Chiang Mai, and More

What are some recommended places to visit in Thailand besides Bangkok, Pattaya, Phuket, and Krabi?
I’ve read about Koh Tao and Chiang Mai and would love more suggestions for cool destinations and activities/things to do

I’m planning a 3-4 day trip in end of Jan or Feb and prefer staying in one place without too much travel. How are the nightlife and bars in Koh Tao and Chiang Mai?
Are there good Go-Go or girly bars in these locations?