Plan to visit China without a visa by exiting for Macao or Hongkong and reenter again.

I hold a Singapore passport. I plan to visit Hainan island for 2 weeks which is visa-free for me. Then, I fly to either Macao or Hongkong for 4 nights and visit Yunnan for 15 days without a visa. I will return to Macao and Hongkong for a few days and then fly to Sichuan for another 15 days without a visa. Is this possible?