Paul A. Volcker will serve the next two years as chairman of the National Commission on the Public Service, his first job since stepping down as chairman of the Federal Reserve. Volcker listed 25 public figures who will serve with him on the panel, which is devoted to winning more respect for government bureaucrats. L. Bruce Laingen, a former State Department officer and one of the Americans taken hostage in Iran in 1979, will be executive director. Others on the panel include Harvard University President Derek Bok, General Foods Corp. Chairman James Ferguson, ex-Sens. Charles Mathias and Edmund S. Muskie, former Vice President Walter F. Mondale, ex-Defense Secretary and World Bank President Robert S. McNamara and former United Auto Workers President Douglas Fraser.