In exchange, the Royals will be receiving Braves' No. 8 prospect Lucas Braun (LHP) and Carter Holton (LHP).
Thomas, 30, is slashing .232/.326/.393 with 10 home runs, 37 RBI, and seven stolen bases through 97 games. Falter, 29, has given up 15 runs on 24 hits with six strikeouts through 9.2 innings in the majors this season. (13.97 ERA).
Both Thomas and Falter are set to be free agents at the end of the year.
Braun, 24, has a 3.53 ERA through 19 games (17 starts) across Double-A and Triple-A this season in the minors. He has given up 93 hits and 27 walks in 94.1 innings, along with 82 strikeouts.
Holton, 23, has a 4.32 ERA with 41 strikeouts in 41.2 innings, giving up 41 hits and 16 walks.