So far there is NO diploma courses in Photography area in Singapore. BTW, why do you really need a diploma. It's just a piece of paper.
What you need it's pure hands on experience with regular shooting. That is more more valuable than a Diploma/Degree/Masters. Although I have a Degree in Photogrpahy but it's the 3 years experience in overseas plus 10 years working experience is where i learn to better myself to be better photographer.
With someone experience to guide you and motivate you that will lead you to become a better photographer. Critic session is where you learn your mistakes. Not just shooting shooting and keep on shooting blindly.
Just like zig mentioned, your client will not be impressed if your portfolio sucks even if you have a Master's in Photography. Correct?