It really depends on what you really want. If you take in Singapore waters, there's only 2-3 dives and half a day that you can practise your skills on. You may not be competent and confident enough if the need arises for you to rescue someone. We have seen some DMs that actually stayed on the boat or swam away when divers almost got drowned on the surface.
I had my RDC on a Kuantan LOB, it was really tough because the instructors can just jump into the water anytime he wants. We have about 7-8 dives and a lot of time in between dives to try out different scenarios and practise them.
Being a rescue diver is not just about getting the cert. Make sure you have enough knowledge and confidence to save someone when someone is drowning or panicking. I would suggest going for a course at Dayang where u have more dives to practice your skills on, or better still, a LOB. I lost quite a bit of weight during my RDC.