He played basketball for Pine Crest School in Fort Lauderdale, Florida, where he was rated a five-star recruit and won a state title.

Thompson bypassed his senior year of high school to sign with development league Overtime Elite (OTE), where he played for two seasons.

[2][3] His identical twin brother, Amen, was born one minute before him; they share the middle name "XLNC" (pronounced "excellency").

[7] Thompson averaged 22.6 points, 7.2 rebounds and 3.4 assists per game, helping his team win the Class 4A state championship.

[12] On May 25, 2021, Thompson signed a two-year contract with Overtime Elite (OTE), a new professional league based in Atlanta with players between ages 16 and 20.

[21] Thompson was selected as Player of the Week for a second time on February 6, 2023, after posting a league single-game record 12 assists, with 17 points and eight rebounds in 21 minutes against the Holy Rams.

[22] At the end of the regular season, he was named OTE MVP and made the All-OTE First Team, with averages of 16.3 points, 7.1 rebounds, 6.1 assists and 2.4 steals per game.

[27] On October 25, 2023, Thompson made his NBA regular-season debut, putting up four points, seven rebounds, three assists and five blocks in a 103–102 loss to the Miami Heat.