Is a HK Working Visa Required

My company sends me to HK twice a year for 3 weeks duration each time to perform site inspections at a customers premises. (every 6 months)
HK Immigration issue me a HK Working Visa, but only valid for 3 entries in that 12 month period.
When I arrive in HK, HKID stamp my visa as 1 completed journey.
If I go into China for sightseeing on the weekend, on re-entering HK, HKID then stamp it as another completed journey. If I do this a couple of times, I use up my allowable 3 entries, and then have to apply for a new one.
My salary is paid for my our Australian based company. I do not get paid in HK at all. Do I really need to apply for it under these circumstances ?