[3] After he left the government in 2003, Hui worked in the banking sector and became a managing director at Hong Kong Exchanges and Clearing for 12 years.

[3] In April 2020, Chief Executive Carrie Lam appointed Hui Secretary for Financial Services and the Treasury, one of the principal officials of the Hong Kong government, even as he remained a member of the DAB.

[11][12] Further to a market consultation, Hui proposed that a licensing regime to be established for Virtual Asset Service Providers (VASPs) in Hong Kong.

Hui is of view that, while protecting investors and safeguarding against money laundering and terrorist financing are the key objectives, the regime will also facilitate the development of a market for virtual assets in Hong Kong.

[16] In February 2021, Hui said that the government would take proactive measures to counter American sanctions under Executive Order 13936, but did not give clear details on how he would do so.

[17] In April 2021, Hui proposed making certain information in the Companies Registry hidden, a move which David Webb said would be detrimental and "How ironic that the government passed a law in 2019 prohibiting face masks in public assemblies so that people could be identifiable, arguably deterring them from committing crimes, but now wants to mask the identities of people trading with the privilege of limited liability, incentivising fraud and corruption.

"[24] Hui and his family own 7 registrable properties, including 4 flats with 3 parking spaces in Hong Kong, 1 in Singapore, 1 in Australia, and 1 in Hangzhou.