Just graduated from NUS with Post-Graduate Degree?
Are you worried about your English proficiency for interview or for teaching?
If you apply to teach Chinese, you don't need to be good at English though it could be a plus. And I believe that if you show enough passion and give good reasons for choosing teaching as career, MOE won't reject you for your English. Chinese teachers are always in demand in Singapore anyway.
Good English proficiency is however a MUST for teaching English subjects.