NEW YORK—The wife of former Goldman Sachs banker Roger Ng on Monday testified in her husband’s defense at a U.S. trial over the looting of hundreds of millions of dollars from Malaysia’s 1MDB sovereign wealth fund between 2009 and 2014. Ng, Goldman’s former chief for Malaysia, is charged with conspiring to launder money and violate an anti-corruption law. Prosecutors say he helped his former boss Tim Leissner embezzle money from 1MDB, launder the proceeds and bribe officials to win business for Goldman. Ng, 49, has pleaded not guilty. He argues that some $35 million he received from Leissner, which prosecutors characterize as kickbacks from the scheme, was actually the proceeds of a legitimate business venture between the two men’s wives. Ng’s wife, Hwee Bin Lim, testified on Monday that shortly after Ng began working for Leissner in the mid-2000s, she invested 48 million yuan—about $6 million at the time—at a …