Speaking to a class on foreign policy on his return to Yale University, former President Ford said today that he regretted not meeting with Soviet author Alexander Solzhenitsyn while he was in office.

"I think in retrospect it would have been better for me to have had him to the Oval Office," Ford said. He said that the lack of an invitation was "not totally a feeling that there might be a policy problem. It was a logistical problem. If we could rewrite history, I would have made some adjustments in my schedule."

Looking tanned and rested, Ford arrived here from Palm Springs, Calif., Sunday night to begin a three-day stay at his alma mater as a guest of Yale Chubb Fellowship. Today he dined with students and participated in a class and several informal discussions.

Ford began his career as a college lecturer in a high-ceilinged, Gothic hall filled with students and reporters. He made no speech, but took questions, and was applauded warmly on entering and leaving.

In response to questions submitted to him earlier by the professor teaching the course, Ford said it was "regrettable" he didn't receive Solzhenitsyn, a 1970 Nobel prize winner and dissident exiled by the Soviet Union in 1974.

Ford indicated his support of the Carter administration's public criticism of treatment of other Soviet dissidents, including Andrei Sakharov.

"The Sakharov issue is a legitimate issue that ought to be raised" in view of human rights agreements reached with the Soviets in Helsinki in 1975, Ford said.

He mentioned his successor by name once, saying he was "delighted with President Carter's appointment of Elliot Richardson" to the Law of the Sea Conference.Richardson, who has held four Cabinet posts, was Secretary of Commerce in the Ford administration.

Ford also said he thought the United States had no obligation to aid in the reconstruction of Vietnam. "At the signing of a 1973 Paris agreemany violations of the accords by that aid might be given," he said. "But since then there have been many violations of the accords by the North Vietnamese, so we have no obligation to proceed."

Ford said the Vietnam war "could not have been considered a success, but we recovered pretty well. Our objective was a right one - to find a peaceful solution to the conflict between the north and the south. The tactics were not the best that could have been used."

He also urged the Carter administration to press for a full accounting of Americans missing in Southeast Asia.

Most of today's sessions were not open to the press, but students later reported that Ford had criticized the media for not reporting more on allegations that congressmen had received cash gifts from the South Korean governments.

Ford also criticized Congress for not accepting his 1974 energy bill, one freshman reported. "He said that if his energy bill had been passed then, the energy shortage could have been reduced by 50 per cent.He said Carter's energy plan is essentially the same as his was then," said Larry Zigerilli.

The former President, who said he would narrate one NBC documentary a year for the next five years, also plans to speak at several universities this year, negotiate a contract to write a book and improve his golf game, students reported.

As a guest of the Chubb Fellowship, Ford is meeting informally with students and faculty. At his request, he gave no public address or press conference. University officials expect that he will return the honorary stipend of approximately $1,500.

The fellowship was established in 1935 by a grant from Hendon Chubb to bring political leaders on campus. Guests are selected by students and faculty, with between five and 10 dignitaries coming to Yale each year.

Former President Truman was a Chubb Fellow in 1953 and Carter was one in 1975. Other Fellows include former British Prime Ministers Clement Attlee and Edward Heath and Portuguese Prime Minister Mario Soares.

Ford's visit has caused only a ripple of excitment on campus. More reporters and Secret Service agents have followd him than students. The sessions with him were open only to undergraduates chosen by lottery. Those who dined with him said they were struck by his candor.