Getting back to Hong Kong

Hi,
I (Turkish) and my girlfriend (Thai) will travel to Hong Kong. As you guys know we are both not required a visa as a tourist for a certain amount of time. However, we will apply for a Single Entry China visa to travel Shenzen for a day trip from Hong Kong.
My question: Is Hong Kong visa multiple entry?
Can I get back to Hong Kong with the same visa on the same day?

Your guidance for this matter would be greatly appreciated.