Thon was a member of the Andorian Imperial Guard in the mid-22nd century.

He was one of the four Andorians on the third raid of the Vulcan monastery of P'Jem in 2151. Thon lay stunned by phase-pistol fire while Shran and Keval fought on with Captain Jonathan Archer and his crew in the catacombs and at last discovered the hidden sensor array. (ENT: "The Andorian Incident")

Thon was played by stunt actor Gregg Sargeant who received no credit for his appearance.
His name comes from the script.
Unlike his fellow three Andorians, Thon's makeup did not allow for his antennae to move.