Hings, who first joined the postal operator seven years ago, reports to director of marketing services Luisa Fulci.
In the role of brand director, Hings led Royal Mail's strategy to retain and gain additional business customers from rivals TNT and DHL, following liberalisation of the postal market in 2006.
Before joining Royal Mail Hings worked in several marketing roles at Carlsberg-Tetley after beginning his career as a junior account planner at Cogent Elliott Advertising.
A Royal Mail spokeswoman said: "Tom has decided that his future career development will be outside of Royal Mail Group and he feels the time is right to seek new opportunities."
In 2008, the brand launched a 'Partners for Growth' marketing push targeting the UK's 4.3 million SMEs.
The above-the-line push, by ad agency Abbott Mead Vickers BBDO, comprised TV, press, direct and digital activity.
Hings also oversaw the launch of Matter, a direct marketing initiative which involved delivery of boxes of free branded goods to consumers. Brands such as Sony, Cadbury and Nintendo were signed up to support the project.