Maybe this information can help you:
Ordinary passport holder of Singapore, Brunei and Japan is exempted from applying for a visa if he or she visits China (mainland) for tourism, business, visiting friends and relatives and enters China by open ports to foreign nationals and stay up to 15 days.
For nationals of these three countries, a visa is requested under following circumstances:
(1) Ordinary passport holder visits China for tourism, business, visiting friends and relatives and stay for more than 15 days.
(2) Ordinary passport holder visits China for the purposes of study, work, official visit, settling down and interview.
(3) Diplomatic and Official passport holder.