Desai, who became regional president for Lowe and Partners in 2010, will remain on until the end of the year and has not decided on a next move.
The departure follows the global merger, announced in May, that created Mullen Lowe Group.
Desai has been with Lowe for 20 years and has run the region for the last five. In his time he worked in India, Dubai, Lebanon, London, Thailand and Singapore.
The move will be seen as surprising given the network's recent success—three Grand Prix at Spikes Asia and Effectiveness Agency of the Year (for Lowe Lintas + Partners) at AMES—as well as the fact that Desai runs not only the Singapore office but also Unilever's global laundry business.
"The last two decades spent across multiple geographies with Lowe and Partners have been great," Desai told Campaign Asia-Pacific this morning. "Over the last five-plus years, we have achieved huge momentum in the region, and I have loved leading the Unilever laundry business ('Dirt is good') globally, the region as well as the Singapore agency."
He added that the network is now a "creative and effectiveness powerhouse", with strong country leaders—almost all of whom are from Asia and nearly half of whom are women. "It's both gratifying and proud to be leaving the network in a far stronger place than I found it," he said. "Leaving so many friends is never easy, but the times ahead promise to be even more exciting."
This is the second departure of a longtime regional agency head to come to light in a week, following last Friday's news that John Zeigler is stepping down to an emeritus role at DDB Asia Pacific. Also this year, Chris Thomas left BBDO Asia to head the Americas, and Chris Jacques departed M&C Saatchi.
Mullen Lowe did not respond to a request for comment by press time.