Aymar de Liedekerke Beaufort, who has spent the last seven years in Asia at the bank, as head of Vietnam, India and most recently South Korea, takes on the newly created role in Hong Kong.
Paul-Antoine Thiebot was previously director, energy transition and sustainable finance, overseeing the banks's regional mandate of the sustainable and positive impact finance group.
The move comes ahead of the law firm's merger with Shearman & Sterling, and adds to A&O's regional presence, where it has offices in Dubai and Abu Dhabi.
Luet, currently head of Citi's Japan Cluster, will oversee Australia, China, Hong Kong, Korea, New Zealand and Taiwan, with Ng retiring after 26 years with the bank on April 5.
Amid wider changes, Roberto Hoornweg, global head, financial markets, and Sunil Kaushal, regional CEO, Africa & Middle East, are to become co-heads of Corporate & Investment Banking (CIB), with Simon Cooper set to leave.