Thomas joins the Latics in a loan arrangement for the season.
Thomas said: "It's a very proud moment for me and my family. I can't wait to get started and meet the fans.
"It was easy for me to come here knowing the Manager has wanted me for over 18 months. I want to do my best and show everyone what I am capable of."
Latics boss Shaun Maloney said: "We are thrilled that Silko has joined us on a season-long loan. He is a very exciting player who can play on the left and right wing, as well as in the number 10 position. I believe he will be well-suited to our playing style this season.
"Silko has represented his country at various youth levels and won Leicester City's Development Player of the Season award back in May. I have been following Silko for the last 18 months, so I am looking forward to him meeting his teammates and working hard to help us achieve our goals."
Wigan sporting director Gregor Rioch also told the club's website: "Silko is someone who we have admired for a long time. We have worked very hard over the summer to get him here, and we believe that Silko will be a fantastic addition to our squad. I am looking forward to seeing how he performs in a Latics shirt this season."