After two trying years in the shadow of the Burt Lance affair, the National Bank of Georgia was jolted again last week by the surprise resignation of its president in a policy clash with Ghaith Pharaon, the Saudi Arabian magnate who bought Lance's majority interest in the bank.

The departure of Robert P. Guyton, 42, who succeeded Lance as NBG's president when Lance joined the Carter administration, apparently caught the Atlanta banking community off guard.

The personable young banker was widely credited with leading NBG out of severe 1977 financial setbacks, while soothing the public relations traumas that quickly followed Lance's departure to head the U.S. Office of Management and Budget.

According to several accounts, Guyton was forced out by Pharaon because of basic philosphical differences over the Saudi financier's priorities for the bank.

"I believe that if you solve problems and improve earnings, growth will occur. That has been my philosophy with the complete backing of the board," Guyton said in an interview. "Pharaon is more interested in increasing the size of the assets."

Guyton said Pharaon told him several weeks ago "that he would like to bring in management that would be more supportive and more responsive to his views." As such, Guyton said, he declined to step aside.

The Nbg board of directors accepted Guyton's resignation last Monday, reportedly with considerable regret. At the same meeting, the directors elected Pharaon's choice as Guyton's successor, Roy P. M. Carlson, a veteran California banker with extensive Middle East business experience.

Until now, NBG has not clearly borne Pharaon's stamp. It partly retains the image that Lance pushed during his 1975-76 tenure as its president -- the Georgia country bank come to the big city.

The selection of Carlson, who has spent most of his 30-year banking career in the international arena, was viewed as a signal that Pharaon is eyeing foreign markets for NBC, Georgia's fifth largest bank.

Several bankers close to NBG affairs speculated that the bank is headed for a period of rapid expansion, reminiscent of the Lance years, which some businessmen here call the era of the "go-go philosphy."

Like Guyton, they expressed skepticism about that approach in retrospect, although Lance's policies had considerable backing at the time.

"Pharaon has seen banks in Europe and other places grow extremely fast and seems to think that banks in the United States can do the same thing," one of the bankers said. "But this is Atlanta, not Saudi Arabia. The American banking industry is much-more-tightly regulated."

NBG also faces special problems, those bankers pointed out. It suffered heavy losses in the wake of the mid-1970s real estate market collapse here. When Guyton took office in April 1977, he cut the bank's costs, wrote off a large portion of bad loans and suspended payments of dividends.

By the 1979 annual meeting, he announced that the bank was back in the black for the second year and ready to accelerate its growth, although the bottom line remained his top priority.

Guyton also dealt frankly with the press and federal scrutiny surrounding the investigation that preceded Lance's indictment on federal charges of bank fraud and conspiracy, stemming in part from his NBG tenure. The former federal budget director is scheduled to go to trial here on Jan. 14.

The bank also came under scrutiny for loans during the Lance era to the Carter family peanut business in Plains, Ga., but a special counsel announced in October that he found no illegality, apparently closing out the last federal probe.

"The bank experienced a period of national publicity and regulatory scrutiny unequalled in the history of banking. We are extremely pleased to report that we survived," Guyton said.

Given the bank's recent progress, several Atlanta bankers close to NBG characterized Pharaon's changes as mysterious. They said he appears to want more control over the bank's day-to-day operation and over the present board of directors, which strongly backed Guyton. Several directors are expected to leave the board by the 1980 annual meeting.

Pharaon also suggested before Guyton's departure that NBG should hire a Pakistani banker to represent Pharaon's interests on a day-to-day basis, but the idea was abandoned after bank officers called it "not in the best interest of NBG," according to several sources.

Pharaon is known to have purchased 80 percent of the bank's stock. He started with 60 percent when he bought Lance's holding in 1978, and at least three of the large minority shareholders recently have sold out to him in light of Guyton's departure.

In addition, he bought almost all of a $3 million limited bank stock issue this year when it failed to sell on the open market.

Pharaon does not serve on the board, but is represented by board member Frank Van Court, a Houston attorney and former member of Republican presidential candidate John Connally's law firm.

"I think he figures that if he was going to put in more money, he wanted more input," one director said. "I guess that makes sense."

Meanwhile, Carlson said in an interview here that he is optimistic about NBG's future, particularly in the international arena.

"This (Atlanta) is an exciting situation, because it does not have a mature international involvement," he said. "I should very much like to have the bank be instrumental in its development."