Upvote:4
Note for future readers: This question is asked after 2022-09-24, when the Hong Kong government lifted the compulsory quarantine requirement for incoming visitors. This is referred to as the "0+3" arrangements. The answer is updated after 2022-11-21, where compulsory PCR testing for inbound travellers is only required on Day 0 and 2 of arrival.
The Quarantine for Inbound Travellers - Frequently Asked Questions page contains the following entries:
A2. Can I leave Hong Kong during the medical surveillance period?
There is no departure restriction on persons under medical surveillance. [... (some exceptions on ongoing travel to Mainland China or Macau)]
C5. If I leave Hong Kong during the medical surveillance or self-monitoring period, will I need to complete the compulsory testing(s)?
During the medical surveillance or self-monitoring period, you must undergo testing(s) per relevant instructions if you are in Hong Kong on the specified day(s) for compulsory testing.
This suggests you are not restricted to leave the region during the self-monitoring period.
Having that said, if you plan to leave before the self-monitoring period (or indeed medical surveillance) is up, you are requested to notify the Hong Kong Government of such. According to one of the emails sent from the Hong Kong Government to inbound travellers:
According to the Government compulsory testing notice currently in force, inbound travellers coming from overseas and Taiwan are required to undergo 3 days of medical surveillance and 4 days of self-monitoring. During these periods, they are required to perform mandatory tests in line with the relevant compulsory testing notice. The Government wishes to remind you some points to pay attention to and the requirement as stated in the relevant compulsory testing notice. If you plan to leave Hong Kong on or before the specified test day, please login to βElectronic COVID-19 Medical Surveillance Systemβ (website https://www.chp.gov.hk/ecmss) to declare your plan.