 On 12 May 2015 he ended his loan and was back to Flamengo again.On 1 June 2015, the Major League Soccer club Seattle Sounders FC announced on their website that Thomás had finished his permanent transfer from Flamengo to the Sounders.Thomás made his debut for the Sounders on 7 June 2015, replacing Marco Pappa as a substitute on 80th minute during the road game against Sporting Kansas City which Sounders lost 0-1.