Thomas recorded a 32-12 mark for the 1925 International League Baltimore Orioles and attracted the attention of White Sox owner Charles Comiskey. Thomas was a workhorse for Chicago from 1926 through 1929, leading the AL in starts and innings pitched in 1927, and in complete games in 1929 (24, for the third straight year). He put together three winning seasons, but was known as a hard-luck pitcher who was never able to win the close ones. By 1930 he was an overworked pitcher who generally couldn’t go past the fifth inning.
On July 24, 1927 Thomas surrendered a mammoth home run to Babe Ruth. It was the first ball to reach Comiskey Park‘s spacious upper deck, which had been installed the previous winter. On August 16, Ruth blasted a Thomas offering over the roof; earlier in the day, Chicago architects had declared that such a feat was not possible at the redesigned ballpark.