Is work visa requied for Australian citizen / company delivering IT services in Hong Kong?

I work for an Australian IT company and we have been awarded a contract to deliver professional services locally to a large HK based company. The work will require multiple trips and around one week per month onsite in HK for around 8 months. Do I need a HKSAR work visa/permit for this work? Can I use the 90-day tourist visa (for multiple entries) in the meantime prior to applying for a HKSAR work visa/permit? Please advise. Thanks in advance.