Need visa if Visit Mainland->Hong Kong , mainland again

Hi i am Singaporean holding an ordinary passport...do i need apply for visa if i make a 15days or less trip to China and then a 7-10days in Hong Kong 7 macua followed by another 15days or less trip to mainland?

That's means i'll be making 2 trips to mainland for 15days or less each and a 7-10days trip in between to hong Kong & Macau