Stephen is admitted to practise as a solicitor of the High Court of Hong Kong, the Supreme Court of England and Wales, the Supreme Court of Queensland, the Supreme Court of Victoria, the High Court of Australia as well as an Attorney-At-Law of the Supreme Court of Jamaica and is the founder of Yap and Lam, Solicitors, Hong Kong. In addition to being a practising solicitor, Stephen is also the Honorary Consul of Jamaica in Hong Kong.
He is also the honorary legal advisor to various New Territories committees and voluntary associations and was the President of the Australian Chinese Association of Hong Kong from 2012 to 2014.