Sydney - Singapore - Guangzhou (5 days) - Singapore - Sydney

No, because this scheme is valid for transit only and your itinerary shows that you will not be in transit, but travel a return trip to Guangzhou. Your segment:

Singapore - Guangzhou - Singapore

Prevents you to enjoy 144 hour visa free transit. However, with just a small effort you could make your itinerary eligible. In other words, your immediate points before and after Guangzhou have to be in two different countries or eligible territories like Hong Kong, Taiwan and Macau. One example of eligible itinerary would be, regarding the most important part of your itinerary:

Singapore - Guangzhou - Kuala Lumpur