By Sumeet Chatterjee and Brenna Hughes Neghaiwi ZURICH/HONG KONG (Reuters) - The announcement by Julius Baer this week that it had hired five senior bankers from Credit Suisse (SIX: CSGN ) underscores the challenge facing Chief Executive Tidjane Thiam as he seeks to reassure staff and investors in the wake of a spying scandal. Preventing staff defections was at the heart of a decision by Credit Suisse to put former international wealth-management head Iqbal Khan under surveillance. But that move -- which spilled into the open when Khan had an altercation on the street with the men who were trailing him -- has by the bank's own admission caused severe reputational damage.