Thex was a male Andorian who, in the mid 2330s, was a Starfleet lieutenant assigned to the USS Barker.

In late 2335 or early 2336, Thex, along with fellow Barker officers Commander Samir al-Halak and Lieutenant Strong, undertook a covert mission to planet Ryn III at the behest of Starfleet Intelligence to investigate infiltration by the Orion Syndicate, and any possible business connections they had with the Cardassian Union. Their presence on the planet was discovered by the Syndicate, and as they attempted to escape Ryn III, they were pursued and fired upon by a Syndicate ship. Thex was injured in the attack, and died soon after due to his injuries. (TLE novel: Well of Souls)

Thex is referred to as a "he", but not identified by any Andorian genders.