The expansion aims to bridge the gap between European luxury brands and affluent Asian customers.
According to Cummings, majority of its APAC growth would be from organic means, but it will also consider potential acquisitions along the way.
The role will not be immediately replaced, with global CEO, Steve Bell, stepping in to take on duties in the region.
The integration brings together more than 8,000 media and performance specialists across 93 key global markets.
Ng, who is Malaysian, has helmed leadership roles at Isobar, Digitas, and BBDO throughout his career.
The transformation programme includes all service lines, functions and central teams, and will initially be led by its largest markets which cover more than 80% of dentsu international's revenue.