You can use more curry paste or add curry powder if you want the spices to be heavier. Different brand of curry paste will have different level of spiciness. I used yellow curry paste that I bought from Thailand. You can fine Dancing Chef in SG, or use Madras Curry paste that can be found at ntuc finest or cold storage.
Chu hou paste can be found at major supermarkets in SG. It is usually placed together with hoisin sauce.