Maybe you can go to Thomson medical and look for Dr Ang Ai Tin. I supposed she is quite good in curing coughing and phlegm. He cured my baby's cough. Infact, we noticed our baby cough even when he was just a new born. His condition is not cured until we go to her when he is about 8mths old. She cleared all our doubt. Before that, we brought him to quite a few doctor but the cough and running nose keep coming back.
One of my niece also got alot of phelgm but she was cured by her method of treatment.
Her charges is high but she is good in diagnosing. I was charged $400+ for my first visit. Given some medicine and vitamin (10 items) for 2 week. His condition really improved so we go back for reviewed and was charged $200+. The third times which is 1 month later, $100+. Now we onlyt go and buy the vitamin from her. And I got a happy boy.