Butler was released by the Royals earlier this week.
Butler will join the Royals organization after Kansas City purchased his contract Wednesday from the Southern Maryland Blue Crabs of the independent Atlantic League of Professional Baseball.
Butler agreed to a contract Monday with the NC Dinos of the Korea Baseball Organization on a one-year, $1 million contract that includes a $200,000 signing bonus, Jee-ho Yoo of the Yonhap News Agency reports.
Butler was sent outright to Triple-A Nashville on Tuesday.
Butler allowed five runs (four earned) on eight hits over 4.1 innings of relief in Tuesday's loss to the Dodgers. He struck out two.
Butler will get multi-inning duty as the Rangers evaluate him as a possible starter, Gerry Fraley of the Dallas Morning News reports. Manager Jeff Banister wants to get a better feel for where Butler may fit in the team's plans.
Butler (groin) allowed one earned run over two innings in Tuesday's loss to the Diamondbacks, which marked his first appearance at the MLB level since April 19.
Butler (groin) was activated from the 60-day disabled list Tuesday.
Butler (groin) made his second rehab appearance at Triple-A Iowa on Tuesday, giving up four runs on five hits and two walks over 1.1 innings.
Butler (groin) was shifted to the 60-day disabled list Monday, Mark Gonzales of the Chicago Tribune reports.