Hales last played for England in March 2019 after he was withdrawn from the preliminary 50-overs World Cup squad that year.
The Guardian newspaper reported he was serving a three-week ban for recreational drug use.
He joins the England T20 World Cup squad as a replacement for Jonny Bairstow (32), who was ruled out of the tournament due to an injury.
Former champions England begin their World Cup campaign against Afghanistan on October 22 in Perth.