Mr So currently heads Investigation Branch 1 of the Hong Kong ICAC, and is responsible for the investigation of public sector corruption and election cases.

He has been with the ICAC for thirty-six years, having joined as an Investigator in the fall of 1976. He achieved the rank of Chief Investigator in 1985, and was promoted to Principal Investigator in 2005 and Assistant Director in 2011.

Mr So was conferred a Master of Social Sciences Degree in Criminology by the University of Hong Kong in 1988. He attended the Stanford Executive Program of the Graduate School of Business, Stanford University in Palo Alto, California, in summer 2006, and the Law Enforcement Executive Development Seminar organised by the Federal Bureau of Investigation in June 2011.

In October 2009, Mr So was awarded the Hong Kong ICAC Medal for Meritorious Service by the Chief Executive of the Hong Kong Special Administrative Region.