PANAMA SHADY BUSINESS Heat is on the top general

In a region known for tolerating shady military men, Panamanian General Manuel Antonio Noriega has long had a reputation for being more corrupt than most. Last week evidence came to light that suggested Noriega's reputation is well deserved. Relying on U.S. intelligence reports, both the New York Times and NBC News detailed charges that the military strongman is involved in smuggling drugs and weapons, laundering money and selling U.S. intelligence secrets to Cuba. Most damning, Noriega, who as commander of Panama's armed forces essentially runs the country, was linked to the September 1985 murder of Dr. Hugo Spadafora, a leading critic of the Panamanian army. It is widely believed that Noriega forced Panamanian President Nicolas Ardito Barletta to resign after Barletta signaled his intention to investigate Spadafora's murder. Barletta's successor, Eric Arturo Delvalle, quickly came to Noriega's defense. Delvalle told reporters that all charges against the army chief had emanated from ''bad Panamanians involved in a conspiracy.'' Noriega, who stood at the President's side, charged that conspirators ''want to get the military out of their barracks.'' The swift denials did little to dampen interest in the allegations. A U.S. congressional committee announced plans to investigate the charges, and others hinted they would follow suit. The pending probes could prove sticky for the Reagan Administration. Charges against Noriega have circulated in Washington for years. The Times reported last week that in 1972, law-enforcement officials in the Nixon Administration proposed to assassinate Noriega in order to help curb Panama's drug traffic. Congressmen will undoubtedly want to know why the U.S. Government continued to associate with a man who was suspected of such blatant corruption. U.S. intelligence officials provided an answer last week. They said Noriega supplied Washington with valuable Cuban intelligence reports, even as he was selling U.S. secrets to Cuba. They also warned that his ouster might disrupt U.S. military and intelligence operations based in Panama. Some Congressmen were unimpressed. Said Representative Charles Rangel, chairman of the House Select Committee on Narcotics Abuse and Control: ''We cannot allow diplomatic concerns to override our efforts to control drug trafficking and abuse.''