A Panamanian citizen claims he was paid $6,000 and promised a permanent-resident visa in this country if he accused Panamanian leader Omar Torrijos of drug-smuggling, gun-running and other illegal activities in an effort to hurt chances for Senate passage of the Panama Canal treaties.

Alexis Watson Castillo told ABC News yesterday that in February 1978 the head of Ronald Reagan's conservative political action group paid him $6,000 about 15 minutes before Watson held a new conference in Miami giving "inside" information about the Torrijos regime.

Watson claimed he was a former Panamanian intelligence agent. Daniel Graham, a former deputy CIA director and retired Army general, assured reporters that he had checked out Watson's credibility through a voice stress test, ABC reported.

Yesterday though, Watson claimed that Graham had prepared the errnoneous statement implicating Torrijos in illicit activities, and then coached him on how to pass the lie detector test, ABC reported.

Watson said he was paid by John Laxalt, Washington director of Reagan's Citizens for the Republic and brother of Sen. Paul Laxalt (R-Nev.).

John Laxalt refused to comment yesterday on Watson's charge. Graham told reporters he believes Watson is lying now and was telling the truth when he implicated Torrijos in illegal activities.

Graham said Watson was changing his story because "he's gone back to Panama and he wants to reinstate himself with the Torrijos government. . . .," the Associated Press reported. Allegations of corruption in the Torrijos government became the main argument of treaty opponents in the Senate and of Reagan, a staunch opponent of the canal pacts.