In order to make room for Thomas on the roster, the Dolphins cut offensive tackle Jeffrey Linkenbach.
The Dolphins added Thomas to the practice squad on Sept. 15 after initially cutting him four days earlier.
The 24-year-old was drafted by the Arizona Cardinals in the fourth round of the 2014 NFL Draft out of Virginia Tech, seeing limited time in two games that season. He was on the Cardinals roster through the preseason before being cut on Sept. 5.
Thomas played in 47 games at Virginia Tech and was named second-team All-ACC in 2011. He finished his college career with 9,003 passing yards, 52 touchdowns and 39 interceptions. He also rushed for 1,359 yards and 25 touchdowns.
Thomas is slated to be the third quarterback on the Miami depth chart behind starter Ryan Tannehill and second-stringer Matt Moore.