Sinnock has previously worked at Ogilvy & Mather London, where he worked his way up to the role of account director on Ford.
He then moved over to the planning side of the business, working at TBWA\London before joining Fallon, where he eventually landed the role of chief strategy officer and worked on the Asda account.
His departure from Asda, only 15 months after he joined, was revealed in June. He was replaced by Jon Owen, who was formerly director of marketing strategy.
In his new role, Sinnock will be based in Singapore. He starts in September and reports to chairman Tim Isaac and chief executive Paul Heath.
Sinnock will be responsible for overseeing the entire planning function in Ogilvy's 29 Asia-Pacific offices.
Heath said: "We look forward to the contribution Mark will make to driving our agenda of producing work for our clients that hit the twin peaks of creativity and effectiveness."
Ogilvy is boosting its planning credentials by boosting senior staff. In Europe it has hired Russell Davis as head of planning for Ogilvy EMEA; Naked's Ben Richards as worldwide head of strategy and integration; and BBH's Rachel Hatton as head of planning at Ogilvy London.
It has also hired Crispin Porter + Bogusky's Colin Drummon and Tim Maleeny from Hal Riney. They have taken heads of planning roles at Ogilvy & Mather West and Ogilvy New York respectively.
Sinnock replaces Paul Matheson, who is moving to New York.