Work is moving along in the expansion of the King’s Hawaiian plant in Oakwood, an effort that could eventually double employment there. The bakery off M. Stringer Road and H.F. Reed Industrial Parkway began operating in 2011 with one production line in a 120,000-square-foot building. A second line began operating in the building this spring, with King’s Hawaiian now up to 300 workers, said John Linehan, the California-based company’s executive vice president.