When Lt. Gov. Lowell Thomas Jr. returned from a visit to South Aftica and said blacks there were "not ready" for the vote, he created a stir among some of Alaska's 9,000 blacks. When he went before the state's Black Caucus to clarify his remarks and said he was against mixed marriages, the matter heated up even more.

"I don't understand it," Caucus president Leroy Williams said Friday after Thomas' appearance. "I had forgotten there were people who thought that way."

Thomas, 54, son of world traveler and radio commentator Lowell Thomas, returned from South Africa last month and criticized the Carter administration's imposition of additional sanctions against the white regime in that country.

At the Black Caucus meeting, to explain his position, he said his remarks about South African economy would "go to hell in handbasket" if blacks were allowed to vote, were not intended to have any political or social significance or any bearing on affairs in Alaska.

He stood by his comment that South African blacks are "not ready" to vote, adding he did not know "when the appropriate time would be."

But the conflict escalated when he told the Black Caucus that he is "not in favor of segregation, but I am against mixed marriage. I suppose that's a form of segregation." He said he believes mixed marriage "goes against nature. It goes against my nature."

Gov. Jay Hammond and Thomas have announced plans to seek re-election in 1978. Although they will run as a Republican team, the governor and lieutenant governor are elected in the primary elections.