Thomas successfully represented Wales at 7s level and was part of the squad that won the 2009 IRB Sevens World Cup, scoring the winning try in the final against Argentina.
Originally from Bancyfelin, Carmarthenshire, the same hometown as Scarlets and Wales centre Jonathan Davies, Aled Thomas made his first appearance in a 2004 Celtic League match against Ulster in Ravenhill. Following spells playing for Carmarthen Quins, Newport Gwent Dragons and London Welsh, he rejoined the Scarlets for the 2011-12 season.
During his last three seasons in West Wales, he has made 63 appearances in the Scarlets jersey with 251 points and consistent performances in the pivotal role while Wales international outside half Rhys Priestland was out with a long-term Achilles injury.
Scarlets Head Coach Simon Easterby said: "Aled has been a valuable and respected senior player within our squad and loyal servant to the Scarlets. He has delivered consistently, proved he's an intelligent and reliable player in terms of managing our game and has established a strong goal-kicking percentage."
"We thank him for his contribution to Scarlets Rugby over the past three seasons and particularly for his work as our outside half leading into the top four and semi-finals of the RaboDirect PRO12 last season. We wish him all the very best with the new opportunity ahead of him."
Aled Thomas said: "I've really enjoyed my time in the Scarlets jersey; it's a great region to be a part of and coming from this part of the world it has meant a lot to me personally to represent the Scarlets. I am grateful for the opportunity to establish myself in senior 15's regional rugby after focusing on the 7s with Wales and the experience of winning the World Cup."
"I'd like to say a big thank you for all the support and advice I've been given by the coaches and for the backing of our supporters in West Wales. I will leave with very fond memories. I've really enjoyed my time here, it's a great group of players and I've improved as a player from the time I've spent at Parc y Scarlets."
The Scarlets have depth at 10 going into next season having signed a new contract with international outside half Rhys Priestland to secure him at Parc y Scarlets, with Steven Shingler back into non contact training and returning to action in a fortnight after a shoulder operation and up and coming Llanelli RFC 10 Josh Lewis, 21, from Ebbw Vale who has appeared for the West Wales region seven times showing impressive form this season including three starts for the Scarlets in the LV=Cup this season against Newport Gwent Dragons, London Irish and Saracens.