New York Times photographer Dith Pran, the Cambodian refugee whose escape from the Khmer Rouge was dramatized in the Academy Award-winning movie "The Killing Fields," announced here Wednesday that he has become a goodwill ambassador for the United Nations High Commission for Refugees. Pran was at a benefit showing of the film at the Avalon theater. He said he will soon travel to Geneva, where he will meet with high commissioner Poul Hartling. He said he may visit the refugee camps in the Horn of Africa. Sen. Edward M. Kennedy gave the opening address at the showing . . .

Therese K. Dozier, a Vietnam refugee and Columbia, S.C., high school teacher, came to the White House Rose Garden yesterday to receive the Golden Apple from President Reagan in a ceremony honoring her as the 1985 National Teacher of the Year. Although the 32-year-old teacher didn't raise the issue with the president, she is opposed to tuition tax credits and merit pay for teachers, two ideas much favored by the Reagan administration . . .

Actress Jean Stapleton, best remembered as Edith in "All in the Family," will give a fund-raising benefit performance of her one-woman show, "The Italian Lesson", in the Kennedy Center Terrace Theater on May 6. The money raised will go to the Women's Research & Education Institute, the research arm of the Congressional Caucus for Women's Issues, of which Stapleton is president . . .

Questionnaires are annoying things. They come unsolicited in the mail and it's hard not to feel a bit guilty when you throw them in the trash. The slick, recently revived Vanity Fair magazine may have found a way of increasing the guilt and getting a filled-out survey returned. A questionnaire, mailed out by the editor Tina Brown seeking a critique of the magazine, came with a dollar bill that her P.S. described as "just a token of appreciation" . . .