Thomas was selected in the first round of the 2011 WNBA Draft by the Seattle Storm. Prior to her rookie season she was traded to the Washington Mystics on April 29, 2011 in a three-team trade deal; with the Indiana Fever receiving Erin Phillips and the Storm's third round draft pick, and the Storm receiving Katie Smith, Jacinta Monroe and the Fever's second round pick. Thomas played for the Mystics for two seasons before being traded to the Atlanta Dream in 2013 in exchange for the Dream's two first round draft picks and a second round draft pick. During her two-year stint with the Dream, Thomas made her first WNBA Finals appearance as the Dream advanced all the way to the 2013 WNBA Finals, where they got swept by the Minnesota Lynx. In 2015, Thomas re-signed with the Dream in free agency. Months later, Thomas was traded to the Connecticut Sun in exchange for draft rights to Brittany Hrynko. In 2015, Thomas became the Sun's starting point guard and started in all 34 games for the first time in her career. In the 2016 season, she continued her role as the Sun's starting point guard; she achieved new career-highs in scoring, assists and field goal shooting. She averaged 11.7 ppg, 5.1 apg while shooting 40% from the field. In 2017, Thomas re-signed with the Sun in free agency. During the 2017 season, Thomas would continue to flourish in her role at starting point guard for the Sun. On June 29, 2017, Thomas scored a career-high of 29 points in a 96-89 victory over the Seattle Storm. On July 8, 2017, the Sun made history as they completed the biggest comeback in franchise history after defeating the Washington Mystics 96-92 after overcoming a 22-point deficit as they improved to 10-7, Thomas scored 15 points along with 6 assists and 5 steals in the win. She was then voted into the 2017 WNBA All-Star Game, making it her first all-star game appearance. Thomas would finish the season setting new career-highs in both field goal shooting and three-point shooting percentage as well as in scoring and steals as the Sun finished fourth place in the league with a 21-13 record, receiving a bye to the second round, making it their first playoff appearance since 2012. In the second round elimination game, the Sun were defeated 88-83 by the number 5-seeded Phoenix Mercury. Thomas scored 15 points in the loss. In 2018, the Sun continued to remain a competitive playoff team. On August 5, 2018, Thomas scored a new career-high 30 points in a 109-88 win over the Las Vegas Aces.. The Sun finished 21-13 with the number 4 seed, receiving a bye to the second round. They would lose yet again in the second elimination game to the Phoenix Mercury for the second year in a row by a score of 96-86. In 2019, Thomas once again re-signed with the Sun. On June 26, 2019, Thomas scored a season-high 19 points in a 74-73 victory against the Dallas Wings. By the end of the season, the Sun were a championship contender in the league, finished with a 23-11 record and the number 2 seed, receiving a double-bye to the semi-finals. In the semi-finals, the Sun defeated the Los Angeles Sparks in a three-game sweep, advancing to the WNBA Finals for the first time since 2005. The Sun however came up short in hard fought five game series, losing to the Washington Mystics 3-2.
Overseas
In the 2011-12 WNBA off-season, Thomas played in Czech Republic for Sika Brno. In the 2012-13 WNBA off-season, Thomas played in Russia for Vologda Chevakata. In the 2014-15 WNBA off-season, Thomas played in Turkey for Orman Gençlik. In the 2015-16 WNBA off-season, Thomas played in Israel for Bnot Herzliya. As of August 2016, Thomas signed with Ramat Hasharon of the Israeli League for the 2016-17 WNBA off-season. In 2017, Thomas once again signed with Orman Gençlik of the Turkish league for the 2017-18 WNBA off-season. In August 2018, Thomas signed with CCC Polkowice of the Polish league for the 2018-19 off-season. In 2019, Thomas signed with Fuheis Blues of the Arab Women's Basketball League for the 2019-20 off-season.
