He graduated from the University of Michigan in 1871. At the same time he studied law and graduated in 1874.
Thayer joined the Library of Congress as an assistant librarian. He was appointed law clerk in the Treasury Department where he remained for ten years before leaving to form the law firm, Thayer & Rankin. He also served as a Judge Advocate General of the National Guard in Washington District of Columbia. In 1909, has was appointed judge of the United States Court for China replacing Lebbeus R. Wilfley.
He served until 1913, when he resigned when investigations were begun into some of the expenses he had claimed.
Rather than face an investigation, Thayer resigned with effect from December 31, 1913. He was succeeded by Charles South. Lobingier
Thayer died on 12 July 1917 of apoplexy in Kingston, New New York
He was buried at Albany Rural Cemetery, Menands, New New York