Larry Thomas, citing personal reasons, resigned yesterday as press secretary to Vice President Bush, a job he had held only since March.

Thomas took the post after Marlin Fitzwater left to become White House spokesman.

Thomas, 39, who directed the 1986 reelection campaign of California Gov. George Deukmejian (R), had been Deukmejian's press spokeman from 1982 until moving to Washington in March.

Before working for Deukmejian, Thomas was a political writer for the San Diego Union and press secretary to then-mayor Pete Wilson of San Diego, now a senator.

Thomas plans to return to California and set up a political consulting firm.

A friend described Thomas as "a dyed-in-the wool Californian who doesn't like the Washington life style." His family lives in California.

For the Bush job, Thomas had been recruited by the vice president's chief of staff, Craig Fuller, a fellow Californian.

In a statement yesterday, Fuller said Thomas "remains a friend and supporter . . . and will be involved in future activities with the vice president from his base in California."

When Thomas' appointment was announced in February, Bush indicated that Thomas would have a role in his 1988 campaign for the presidency.

"He brings a dimension of political campaign experience and judgment that will be an asset to us," Bush said at the time.

Yesterday Gayle Fisher, speaking for the vice president, said Thomas "will help on the campaign."

Thomas told a friend that he expects to have Bush as a political client.

Rich Bond, Bush's deputy campaign manager, said of Thomas, "We are sorry as a group to see him go. He'd been playing a key role in the operation, and we hope he will continue to do so from California. He's very plugged in out there."

Bush's deputy press secretary, Steve Hart, has been named acting press secretary.

Barbara Pardue, who has been press secretary for the National Republican Congressional Committee, assumed the role of press secretary to Bush's presidential exploratory committee this week.