According to Chad Graff of The Athletic, Thomas pleaded guilty to a fifth-degree marijuana charge after being arrested in January in possession of 143 grams.
The 23-year-old was an undrafted free agent last season who appeared in five games in 2018. He totaled 30 rushing yards on eight attempts during his rookie campaign.
He was especially valuable in providing depth when Dalvin Cook was limited by injuries, also helping out on special teams. Once Cook returned, Thomas was moved to the practice squad.
The running back will go into 2019 hoping to earn a role once again on the Vikings roster, although there will be plenty of competition. Ameer Abdullah, Mike Boone and rookie third-round pick Alexander Mattison will all try to get playing time behind Cook.
Thomas will still have a chance to impress the coaching staff this summer as he is able to participate in training camp and preseason games, but his suspension will begin Week 1 and he won't be allowed to return to the team until Sept. 23.
This could potentially hurt his chances of making the 53-man roster this season.