South Africa's dramatic return to the U.N. General Assembly after a five-year absence ended quickly today when the assembly voted once again to reject the credentials of the South African delegation.

As soon as the final results were in - 93 to 19, with 11 abstentions - the South African representatives rose and left the assembly hall.

Everything about the event - the return, the ouster, the departure - had been planned to advance. The South Africans had even consulted the U.N. camera crew to ensure that it followed their progress out of the hall, the long way around. By prearrangement, the proceedings were transmitted by satellite to South African television.

South African Ambassador J. Adriaan Eksteen denounced the assembly action. At a press conference after his exist, he attacked the move as "infamous" and warned that "the denial of the right to be heard had frustrated that degree of understanding [between the United Nations and South Africa] which is essential to any form of collaboration whatsoever."

He said, however, that South Africa is still "standing by" the Western proposal for U.N.-supervised elections in Namibia (Southwest Africa), should certain "deviations" from the original plan be resolved. It was not, he said, the end of the road for the negotiations on Namibia, but "we're coming close to that point; we're getting sick and tired of this."

Western diplomats who have been negotiating a compromise agreement on independence for the territory for more than two years said that the South African performance was a further indication of Pretoria's determination to deadlock the U.N. plan without being blamed for the stalemate.

It was an effective way, the diplomats said, to play over the heads of Western governments to a public opinion in expectation that it would react negatively to the assembly's refusal to let South Africa give its side.

The South African action also served to distract attention from the drive by African nations to organize economic sanctions against South Africa because of its intransigence on Namibia.

U.S. Ambassador Andrew Young, who joined 18 other Western delegates in voting against the ouster, warned that the United States "does not accept that anything that has happened here today can constitute any excuse on the part of anyone for failing to cooperate in the effort to find a peaceful and just solution to the question of Namibia."

Young also defended the principle that U.N. bodies should include all countries no matter how different their views. He noted that in the years that the United States barred U.N. membership for China "we found ourselves constantly shedding the blood of our people because of our inability of communicate with people with whom we disagreed."

South Africa had been ousted from the assembly in 1974 on the ground that its government did not represent the majority of its citizens.