Thembekile Enoch (Twiggs) Xiphu, a South Africa exile, is deeply afraid to go home again. He fled his native land seven years ago, crossing its border by foot, after a harrowing journey, into neighboring Botswana. He also traveled by train and automobile, all the while trying to escape detection by the South African Security Police. His memory was vivid with the tortures he had just endured for his role in trying to improve science education in his people's schools and his antiapartheid work with other students.

Twiggs was one of thousands of South African students who became refugees after the 1976 Soweto rebellion, which left about a thousand African youths dead and prompted the exile of thousands. After being jailed in South Africa for two months, he spent six months in a U.N. refugee camp and came to the United States as a scholarship student at Howard University. He has been an exemplary student and an antiapartheid activist.

Because of his torture and knowledge of other South African terrorist practices, Twiggs applied for political asylum in the United States. But for the past three years his pleas have been turned down by the Immigration and Natural- ization Service (INS). "I feel so frustrated," said Twiggs. "I have been a good student, always on good behavior, never engaged in violence of any kind, but I am being denied asylum in the land of the free."

Twiggs' friends and lawyers fear that if he is returned to Southern Africa, he will meet imprisonment or death. "He speaks out against South Africa," said William T. Jones of the Commission for Racial Justice. "He was a member of the banned black consciousness movement. He is one person on a list South Africa wants."

Twiggs first petitioned for political asylum in October 1981. His request was denied, and he was ordered returned to Botswana. A penniless student, he approached the Lawyers Committee for Civil Rights Under Law, which has since represented him.

"It is generally recognized," said his attorney, Carolyn Waller, "that the government of South Africa is one of the governments which does pursue opponents across international boundaries and that the situation between the South Africa and the front line countries is particularly tense . . . . Twiggs has a well-founded fear of persecution should he be returned to South Africa, and he could not be safely returned to Botswana." Waller calls Twiggs' situation "life-threatening." But repeated pleas for asylum have been denied. His three-year battle reaches a climax April 9 when once again he appears before INS.

Twiggs' problems with the South African government go back a dozen years to his student days at Fort Hare University, where he fought to improve educational opportunities for his people in a country where about 40 percent of the people are illiterate.

He was a founding member of the Association for Science and Technology, an organization devoted to obtaining science laboratories in school. He also belonged to the BCM organization, the South African Student Organization founded by the late Steve Biko and banned in 1977. During the 1976 Soweto rebellion, he was a student leader.

It was for these activities that the South African Security Police arrested Twiggs in October 1977. Placed in solitary confinement, he was subjected to repeated torture. The police beat him with rubber hoses that had metal springs.

One day they came into his cell, placed a hood over his head and hung him by his feet for an hour. In order to question him on another occasion, they held him by his legs from the ledge of a 10-story building, and on yet another occasion security police forced straight pins under his fingernails and through his fingers.

This imprisonment ended after two months; it could have lasted two additional months under terms of the terrorist law that the police used to arrest him. Twiggs' parents were harassed both while he was in prison and after his release. It was then that he fled to Botswana.

After living under the heavy cloud of pending deportation, Twiggs is fearful as he once again nears the date when he must convince the INS that it is dangerous for him to return to his home.

"I'm afraid." he said. "When you are a refugee, it is a struggle to leave your country. Then you resettle. But the thought of possibly going back to South Africa makes me fear for my life. I begin now to think of all the terrible things even though I'm out. Sometimes I dream I am still in detention, and I just shudder when I think about going back." But now there is yet another concern. "Every time I see something that says INS, my heart just jumps a beat."