A southern province of the planet Andor, found on the Southern Archipelago. The region is reknowned for its festivals and celebrations, including the Spring Water Festival.

Thelasa-vei is home to the clans Cheen and Thitar who reside within Cheen-Thitar Keep. (Star Trek: Deep Space Nine novella: "Andor: Paradigm" (Worlds of Deep Space Nine Vol. 1)