Where to go for 3/4 days from Bangkok for NY, or stay there?

[futuremoneyinbank]

Looking for ideas for NY. We have plans for 10 days prior to this travelling around Thailand but only as far south as Hua Hin. I've added a few days on the end of the trip for us to relax or explore more but am now over thinking about whether we should stay in Thailand and visit Krabi or Koh Lanta (for eg) for relaxing beach vibes or fly to Singapore and see the high tech "super trees" at the Singapore Gardens and relax for a few days elsewhere to make the flight more worthwhile. Or if stay in Bangkok or Hua Hin for the extra few days over NYE, is there anything/where special you'd recommend seeing? We fly back to UK from Bangkok. Does anyone have any suggestions/experiences of NYE in Thailand?

The Nests in Chang Dao. Such an amazing place with fantastic food. Nest 2 is better accomodation.

We are actually already doing Chang Dao, Chiamg Mai, Kachanaburi and Hua Hin as well as 2 nights in Bangkok, so I feel we might want some down time. Not sure whether to head to Koh Lanta from our 2 days in Hua Hin then back for another night at Bangkok before home on the 2nd. Just wondering what the vibe is in each place for NYE and if anyone has specific recommendations really!