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 as well as the High Court of Australia and is the founder of Yap and Lam, Hong Kong. In addition to being a practicing solicitor, Stephen is also active in providing service to his fellow legal fraternity by serving as the Convener of the Australian Interest Group as well as a Member of the Standing Committee on External Affairs of the Law Society of Hong Kong from 2009 to 2015.
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.