Thomas St. Leger Moncure, 55, a retired research analyst with the Defense Intelligence Agency, died of cancer Tuesday at Suburban Hospital in Bethesda.

He had retired last year after 30 years of service that began with Air Force intelligence.

Mr. Moncure was born in Ruther Glen, Va. He came to Washington with his family as a boy and graduated from McKinley Technical High School.

After attending Virginia Military Institute for two years, he joined the U.S. Army as an infrantryman and participated in the Battle of the Bulge in World War II.

After the war, Mr. Moncure earned a degree in government from George Washington University. He sang in the Glee Club there and was 1948 national individual collegiate champion as a member of the Rifle Team.

He had been active in the National Capital Area Council of the Boy Scouts since boyhood. An Eagle Scout, he received the District Award of Merit in 1973 and the Silver Beaver Award in 1974. He had served as district commander of Area III of the Potomac district.

Mr. Moncure was a member of the choir of Christ Episocpal Church in Rockville for 30 years.

He is survived by his wife, Ruth T. and a son, Robert T., both of the home in Rockville; another son, Thomas St. L. Jr., of Gaithersburg; a daughter, Ruth M. Biser of Frederick, Md.; two brothers, John P., of Silver Spring, and William O., of Falls Church; a sister, Mary B. Moncure of Los Angeles, and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to the choir fund of Christ Episcopal Church.