When President Reagan, in the middle of last night's news conference, pointed to the rows of reporters seated before him and called out, "Bob Thompson," Robert E. Thompson, Washington bureau chief for the Hearst newspapers, was watching it on television at home.

In the suddenly silent East Room of the White House, no one stood to ask a question until the president finally pointed to another reporter, who quickly picked up the questioning. Afterward, a White House press aide said Reagan had promised to call on Thompson.

Thompson said later at home here that he was surprised to hear his name called after he had informed the White House press office that he would not be there. He said he stood up in his living room and burst into laughter.

"I was as surprised as anyone else," said Thompson. "I've been to more than half of his press conferences and he's never called on me. Suddenly I'm sitting at home and he calls on me. I stood up anyway."

Later, Reagan pointed to a reporter and said "Al." No one named Al was seated in the area, but another fast-thinking reporter jumped at the opportunity.

The incidents exposed some of the orchestration of the president's news conferences. The names Reagan called out were on a seating chart on the stand in front of him in a prearranged order in which he was supposed to call on reporters. Afterward, however, no one knew who "Al" might be.