SINGAPORE—The head of Asian operations for Swiss bank BSI SA, Hanspeter Brunner, has “decided to retire,” the bank said on Tuesday.

The company didn’t give a more specific reason for the departure. And the 64 year-old Mr. Brunner, who is a BSI board member based in Singapore, didn’t respond to a request for comment.

The Swiss bank on Tuesday said Mr. Brunner’s responsibilities will be handed over to its Head of Private Banking Asia Raj Sriram.

BSI, which is based in the Italian-speaking region of Switzerland, historically catered to Italian clients. BSI then relied on Mr. Brunner to aid its expansion in Asia, after he joined the bank from the Singapore office of RBS Coutts in 2009.

In early 2010, BSI said Mr. Brunner’s appointment was an important part of its increasing presence in Asia. The following year BSI said its number of employees in Asia had increased to 280 from 50 over the course of a year and a half.

One of BSI’s major clients—Malaysian state investment fund 1Malaysia Development Bhd., or 1MDB,—is under corruption-related investigation in Singapore and other jurisdictions, including Malaysia and Switzerland. BSI hasn’t been accused of wrongdoing in those investigations.

Switzerland’s attorney general said in January that his office’s investigation into transactions involving 1MDB showed $4 billion may have been misappropriated from Malaysian state-owned companies.

1MDB said at the time that it was prepared to cooperate with authorities, and it has denied wrongdoing. A representative for 1MDB on Tuesday didn’t respond to a request for comment.

Last year Singapore police told Malaysian authorities in a letter reviewed by The Wall Street Journal about more than $500 million in transfers made between 2011 and 2013 from an entity tied to 1MDB into a BSI account. 1MDB has acknowledged it holds a BSI account in Singapore. BSI has declined to comment on the matter.