South African tried unsuccessfully today to reclaim its General Assembly seat, which was revoked in 1974, as the U.N. body took up a resolution calling for sanctions against Pretoria.

The assembly voted 112 to 22, with six abstentions, to reaffirm its 1974 decision rejecting the credentials of the South African delegation. It then opened a debate scheduled for five days on the territory of Namibia, which remains under South African rule.

The United States voted with the Western nations and Israel against the ouster of South Africa, affording U.N. Ambassador Jeane Kirkpatrick the opportunity of delivering her maiden speech in the chamber. She opposed the assembly's denial of South Africa's right to participate in the debate and called it a question with "substantial implications for the United Nations."

The suspension of membership under the guise of a credentials issue, she said, is an act "that lies beyond the power of the assembly."

This was the same postion the United States took in 1974 and in May 1979 -- the last time that South Africa tried to return to the assembly. m

Today's vote reaffirms the procedural status quo. South Africa cannot sit, speak or vote in the assembly, but it retains its U.N. membership with the right to participate in Security Council debates and to keep a permanent mission at U.N. headquarters. Only the Security Council can suspend or revoke full U.N. membership.

Western diplomats involved in the long and frustrating effort to negotiate independence for Namibia under U.N. supervision contended today that South Africa's motive in forcing the assembly issue was to dramatize its contention that the United Nations cannot play an impartial role in Namibian elections.

South Africa blocked the independence process at a U.N. conference in Geneva two months ago, and today's resumed session of the 35th General Assembly was a reaction to that stalemate. The African nations intend to press for a vote in the assembly and then the Security Council, which will force the Reagan administration to take a stand on African policy for the first time.

The African nations, in pressing South Africa's original ouster from the assembly in 1974, argued that its delegation was not representative of the vast majority of the population.