I did two and a half weeks in North Sulawesi/Bunaken Island in Indonesia and would definitely recommend that as a great dive trip. I flew into Manado from Kuala Lumpur (you can also fly there from Singapore) stood for a few days in some rustic accomodations and did a few days of rain forest trekking in Tangkoko Nature Reserve. From there you could dive the Lembeh Strait (I didn’t but regret not doing it) which is some of the best muck diving in the world, and then you could dive the Bunaken Marine Reserve (which is phenominal). If you have any questions, don’t hesitate to ask, I’d be more than happy to share other specifics of my trip if interested.