Okay. For a Long weekend. I will say Cebu,Philippines. But it's hectic. Here is how it will go.
Assuming the Friday is an holiday.
On Thursday midnight, take a Cebu pacific air flight from Singapore to Cebu. U will land around 0400. Then u can travel to moalboal in Cebu. About 3 hour drive. U can dive on that day itself. They have sardines ball right in front of the coast. No need a boat ride. Then afternoon u can get 1 or 2 boat dives. That is for Friday. I didn't do any night dive but u can try
.
Saturday. U can do 3 dives. Then u are done.
Sunday, u can take the latest flight back around 2000. Landing In Singapore at around 2359. Or u can spend the morning and go snorkeling with whale shark at Oslo. Abt 3 hour away from moalboal. Then u can have some food at Oslo and then take a quick shower and then head to the airport or city. Remember to to free dive when u snorkel with the whale shark. I will get to the city early and hang around the airport. There is a casino righty across the airport.
and if u are packed light. U can hang around town.
So u can do 4-5 dives and still able to clear 24 hours before u fly.
I dived with savedra dive centre. Good organise outfit with the rooms right across their dive centre. Btw. 8 and 9 Feb is public holiday in Singapore. U can do sipadan, but space and tic will be booked up or expensive.
Pm me if you have any questions.
Since u ask Indonesia, I will comment on that as well.
Batam which is Abt a 45 min ferry ride from Singapore is okay.. And probably same dive viability as in sg. Marco stuff and 1m visibility. Lots of macro though.
Most people usually travel to manado/Lembeh. By either Garuda or SilkAir. But they do not have daily flights. So everyone tends to stay a week or so. And everyone dunmind as the diving is great there!!
Other places will need a few flights away.
Malaysia. The north part of Malaysia is okay during Feb. Ie Sipadan. The usually spot during that time like Tioman in Pahang is not too good.