Former president Ford received a $10,000 fee from a South African lobbyist last year for addressing a seminar on business opportunities in South Africa, it was learned yesterday.

Richard Wennekamp, special assistant to Ford, said the former president accepted the fee only after being assured that no funds had come from the South Africa government.

Ford gave the speech June 29 in Houston at a lucheon arranged by Sydney S. Baron Inc., a New York public relations company, Wennekamp said. The company is one of the largest of 20 registered lobbyists and agents for South Africa in the United States.

In a telephone interview from Palm Springs, Calif., Wennekamp said the $10,000 fee for a luncheon speech was "a top figure" for Ford but not unusual.

Wennekamp termed "totally ridiculous" allegations published in the South African press last weekend that secret funds from the South African Ministry of Information had gone into Ford's unsuccessful 1976 campaign.

A South African commission is investigating charges that Eschel M. Rhoodie, formerly the highest ranking civil servant in the Information Ministry, spent $37 million on covert projects to improve South Africa's image in the United States, Britain, West Germany, Japan and other countries.

Ford had been invited to speak at the seminar by former representative Seymour Halpern (R-N.Y.), a vice president of Baron, Wennekamp said.