You may be eligible to apply for the Working Holiday Scheme if you are 30 or under. Visit the government
https://www.immd.gov.hk/eng/services...ay_scheme.html
I feel that anyone who is thinking of entering the teaching profession, especially those who teach young learners, should have recognized teaching qualifications. In my opinion, the best teachers should be in primary schools but I do not have time to go into why.
Some people think that just because a person is a native speaker and writer of a language that he/she can teach it too. This is not always the case and many unqualified native speakers of English who start teaching English soon realize that it is not as easy as they thought. German and Mainland Chinese learners of English, in particular, often have a better knowledge of English grammar than some English speakers themselves!
I would always prefer to employ a local Hong Kong teacher who has excellent English (and many of them do) and who has teaching qualifications to a native speaker who has no related qualifications and no experience. Many local English teachers have master degrees in English language subjects, and to work at most universities in Hong Kong, lecturers need a master’s degree and most likely a PhD.
It is unlikely that a native English speaker who has no qualifications or possibly a related undergraduate degree would be employed as a teacher by government schools or any of the Hong Kong universities. However, there might be a possibility as a Teaching Assistant in a school. I am not sure. Am I right in thinking that unless you are married and on a dependent visa, people would not be able to work part-time? You can check this out with the Immigration Department.
If you are going to work with children under 18, it might be worth obtaining a DBS (Disclosure and Barring Service) check before you come.
Good luck.