WASHINGTON, D.C. (CPS)- Revelations of the complicity of Saigon and the Central Intelligence Agency with 80% of the world's opium i f rom Laos last week brought swift denials from South Vietnam's Vice President Nguyen Cao Ky and the CIA's director Richard Helms, and paved the way f or possible hearings on Capítol Hill. Ramparts Magazine's May issue detailed the network of hard drugs in Southeast Asia, from the Laotian Plain of Jars to the arms of U. S. servicemen. Sen. George McGovern first brought attention to the article's charges in a statement April 14, noting he had sent letters of inquiry on the matter to Sec. of State William Rogers and CIA director Helms. He has received no response to his inquiries. That afternoon, in his first public speech, Helms opened his address to the Amfirican Society of Newspaper Editors with an impromtu and unequivocal denial of any involvmant of the CIA with the world drug trade. Characteristically, he was not more specific. Also that afternoon in Saigon, Ky had a press conference and, referring to Mc Govern's charges called the Senator a "member of the international communist conspiracy. " The U. S. commercial media has made only brief mention of the story.