It was a four-point game (46-42) six minutes into the second half, but Arkansas State's 11-point run -- with five from Reed and two treys from Johnson -- pushed the Red Wolves ahead 57-42 with 12:32 to go. The Muleriders were unable to get closer than 13 for the rest of the contest.
Reed finished with 19 points and Johnson scored 16 as Arkansas State finished on 27 of 56 shooting. The Red Wolves (7-4) racked up 29 points on free throws after shooting 88 percent from the line.
Southern Arkansas (4-4) got 44 of its points from the bench, with 17 coming from Jeffrey Walker and 16 from Chauncy Williams.
Arkansas State faces off in Sun Belt competition against Texas-Arlington on Thursday.
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.