Since you want to apply for NUS Chem PhD Programme and claim that you are a good self-directed student, I believe I can assume you can understand my answer in English.
要是题主接下来的回答看不懂，我建议还是不要申请了，因为NUS也是有托福/雅思要求的
National University of Singapore (NUS) is a research-intense university, which values students' both academic and research capabilities. Therefore, since you are from a decent university in China P.R., as long as you have good publications during your undergraduate/master study, preferably in English, and GRE & English Qualification Results, why not just apply for it?
Some prerequisite for NUS PhD programme
At least second upper-class degree for undergraduate study
Good GRE & EL qualification
Others are based on case-by-case study
Side note: They also offer PhD student good scholarships, which covers your tuition fee & provides you a monthly stipend of 2.5K SGD
