His appointment is understood to mark the first time an Asian creative will have global responsibilities.
Tham is the second senior Ogilvy executive to leave Asia for the US. He will join global chief executive officer Miles Young, former Ogilvy Asia-Pacific chairman, at the network's New York office on 1 January.
"Miles and I have seen some successes, both business and creative. The challenge now is to get right up to the top of the tree globally," he said.
The question of who will follow in the footsteps of Tham - a pillar in the Asian creative industry - will be hotly debated. "We have a lot of good people internally, and an announcement will be made shortly," he noted.