I'm with people who recommended Bali as well. Went a few years ago and started from near Kuta and moved all the way north to Lovina. Had the opportunity to visit/hike to Temples, swam with the dolphins, visit art galleries, visited a Balinese village (my guide invited me to his home for dinner), etc. I flew on Singapore which was amazing. It's all about flexibility as far as your dates and getting seats.

For a shorter visit have you considered Central America e.g., Honduras or Costa Rica?