Robert J. Plaud, 56, of 46 Wellington St. died yesterday in St. Vincent Hospital after being stricken. He leaves his wife, Debra (Trainer) Plaud; a daughter, Donna Marie Plaud; his mother, Alberta (Fisher) Plaud Travers; two brothers, Albert E. and Ernest E. Plaud Sr., all of Worcester; two sisters, Louise Barrett of Worcester and Leah Rice of Oxford; nieces and nephews. He was born in Worcester, son of the late Philip Plaud, and had lived here all his life.         Mr. Plaud was a laborer for Astro Foam in Holden for the past five years. He was a member of Notre Dame des Canadiens Church.     The funeral will be held tomorrow from Alfred Roy and Sons Funeral Home, 12 Hammond St., with a Mass at 10 a.m. in Notre Dame des Canadiens Church, Salem Square. Burial will be in Worcester County Memorial Park, Paxton. Calling hours at the funeral home are 6 to 9 tonight. The family requests flowers be omitted. Memorial contributions may be made instead to the American Heart Association, 23 Midstate Drive, Auburn, 01501.