Asia's swelling ranks of the mega-wealthy are proving to be a mixed blessing for Morgan Stanley.

The firm's Asian private banking unit has boosted assets under management and revenue this year, according to Mr Vincent Chui, who oversees the business. But because top bankers keep getting poached by family offices set up by the richest people, a plan to increase headcount has fallen flat.

At least 10 relationship managers left this year for family offices, leaving headcount in Hong Kong and Singapore unchanged from the end of last year at about 100, Mr Chui said in an interview.

Morgan Stanley's earlier plan was to add 20 this year, he said, adding that some others left by what he described as "natural attrition".

The Asia-Pacific region's 42 family offices, which oversee US$445 million (S$602 million) on average, are luring top relationship managers from private banks with the prospect of higher pay, more varied work and a bigger influence in decision making, according to Campden Wealth.

The number of managers running offices for ultra-rich families cannot keep up with the region's expansion of wealth, said Dr Rebecca Gooch, London-based Campden's head of research.

Private banking arms of UBS Group, Standard Chartered and Deutsche Bank have also been boosting headcount in Hong Kong and Singapore.

Mr Chui said he chose to wait out the rush to obtain talent at all costs that peaked earlier this year, but remains determined to add staff.

"Given the irrational exuberance of hiring relationship managers in 2016 and the early part of 2017, we preferred not to participate in the bidding game," he added.

"With banks now focusing more on costs, notwithstanding good revenue growth, it's time for us to step up the quest for talent."

Chief executives at a family office in Asia can demand greater pay because there is a shortage of top professionals running such operations in the region, where the industry is less mature than in Europe and North America, Dr Gooch said.

They also tend to help the family run its business as well as manage its wealth, she added.

Total annual compensation of family office CEOs, including salary and bonus, averages US$362,000 (S$489,000) in the Asia-Pacific region, according to the Campden Wealth report.

A senior relationship manager's pay is at least $230,000 in Singapore, according to the 2017 Robert Half salary guide.

BLOOMBERG