The jury in the Vietnamese espionage trial in Alexandria interrupted its deliberations yesterday to ask the judge if Ronald Humphrey would bave to know that David Truong was a Vietnamese agent in order to aid and abet Truong in any alleged espionage plot.

Humphrey is the United States Information Agency employe who is accused of stealing cables and giving them to Truong in what Humphrey said was an effort to improve relations with Vietnam and get his common-law wife out of that country.

Truong, a Vietnamese expatriate whose father once as a peace candidate against Nguyen van Thieu, is accused of passing the cables through a courier - who testified she was a government agent - to Communist officials in Paris.

Judge Albert V. Bryan answered "yes" to the jury's question, which came during the first day of deliberations in the case.

The jury recessed at 7:30 last night and planned to resume deliberations today on the charges that Humphrey and Truong committed espionage, conspiracy and other crimes on behalf of Vietnam.

Midway through deliberations yesterday jury foreman Robert Charlesworth, a retired executive of the American Telephone and Telegraph Co. sent Bryan a note requesting clarification of four of the jury instructions they received yesterday.

In addition to the "aiding and abetting "question the jurors asked Bryan to define the terms "agent and representative" that are used in the indictment. A person who acts on behalf of a government with its authority is an agent. Bryan said. An agent and a representative of a foreign government are the same, he said.

Jourors, also asked whether the judge's instructions given to the jury yesterday morning meant that the government had to show both an intent to injure the United States and aid a foreign nation on the part of Humphrey and Truong Bryan said only one of the conditions had to be met.