If you are looking for enjoying breath-taking natural beauty (crystal green waters, white sand, waterfalls, hilly roads) in the daytime & party the night away like never before, Koh Samui is your best bet!!
We visited Samui last winter during our honeymoon & we realized there’s something for everyone in this tiny island. Here are some highlights of Samui:
Stick to Chaweng would be my advice, as other beaches like Lamai or Bo Phut or even Chiang Mai are cut-off & rather deserted. The corollary to that is that Chaweng properties are also the most expensive!
Hire a bike - that’s the best way to travel & advisable to rent these from your hotel, as the local vendors ask for your passport for deposit
Try to get a hotel as close to Chaweng as possible. We stayed at the quaint Blue Lagoon on Chaweng, possibly amongst the most hospitable hotel staff you’ll ever come across - that has a peaceful tranquility you’ll love & is yet located just 5min walking distance from all the action
Try the local food - seafood at its best, & gorge on fruits you’ve never seen before (& won’t find in Bangkok either!)
Be a little careful when entering nightclubs, esp. if your group comprises women - as many of these places are ’pick-up joints’. Oh yes, many gay/ transvestite bars here too, so the men need to be careful too!
Go for Samui - the memories will last forever!