Following graduation from Cornell University in 1982, Thomas joined AT&T Bell Laboratories in Princeton, New Jersey, working as a Senior Member of the Technical Staff.

He left AT&T in 1987 to work for Lockheed Engineering and Sciences Company in Houston, Texas, where his responsibilities involved reviewing materials used in Space Shuttle payloads.

From July 1999 to June 2000 he was Director of Operations for NASA at the Gagarin Cosmonaut Training Center in Star City, Moscow, Russia.

[3] In his last assignment, he served as the International Space Station Program Scientist overseeing NASA experiments performed on the ISS.

During the STS-70 mission, Thomas was responsible for the deployment of the sixth and final Tracking and Data Relay Satellite from the Space Shuttle.

The STS-83 Microgravity Science Laboratory (MSL-1) Spacelab mission, was cut short because of problems with one of the Shuttle's three fuel cell power generation units.

[3] In 2013, Thomas wrote a book with the assistance of Mike Bartell, "Orbit of Discovery: The All-Ohio Space Shuttle Mission,"[5] referencing the STS-70 flight.

[3] In July 2014, Thomas, now a retired astronaut, was featured as a celebrity visitor to the spaceship R. U. Sirius in the comic strip Brewster Rockit by Tim Rickard, which is anachronistically set in the present time.

The same woodpecker appears, pecking at the windows of the spaceship, at which time Thomas confesses that he owes the bird money.