Thomas is rated 18th overall on the ESPN 100 for 2020 player rankings, and he's the fourth-ranked shooting guard on the list.
Head coach Will Wade has thrived on the recruiting trail since joining LSU ahead of the 2017-18 season. Thomas becomes the Tigers' fourth five-star prospect in the last three classes.
"Coach Wade was very consistent in the recruiting process," Thomas said, according to ESPN's Jeff Borzello and Biancardi. "Always staying in contact with both me and my mother. We are very close. Her being comfortable was important to me.
"When we visited back in September, we watched the team practice - got to know the guys on the team more. Since then they have been in constant contact with me or my mother every day. His consistency in the recruiting process was a big difference."
Thomas is one of the best pure scorers in next year's recruiting class. He topped the Nike EYBL circuit with 29.5 points per game during the regular season.
The Oak Hill Academy product joins three-star prospects Jalen Cook and Bradley Ezewiro in LSU's 2020 class.
"Coach Wade lets his guards play," Thomas said. "Their plan is for me to come in and score points and make plays. That's what I do."
UCLA was also in the running for Thomas' services.