The bank said Flint will become chief executive of the wealth management unit on 1 January, one of the bank's four global businesses. Previously known as personal financial services, the unit has more than 50m customers and made an operating profit of $4.3bn (£2.6bn) last year, a fifth of the group.
Flint, 44, joined HSBC in 1989 and has worked in Hong Kong, Singapore, Indonesia, Thailand, India, Bahrain, the United States and Britain. He has been head of strategy and planning and chief of staff to the chief executive since the start of this year.
Guilherme Lima, who joined two years ago from McKinsey as group head of strategy, will take Flint’s role.
Stuart Gulliver, group chief executive, is restructuring HSBC to cut costs and axe unprofitable areas to lift returns, which has seen several changes in senior management.
Gulliver said Thurston, 59, had wanted to retire two years ago but stayed on to manage RBWM during the reorganisation.