Calvin Sims, a former MARTA employee who previously ran in commission and CEO elections, has also said he will enter the race.
Interim CEO Lee May announced earlier this month he will not seek election to a full term to the office. Another potential candidate for the CEO's seat, retired DeKalb Sheriff Thomas Brown, said he would not enter the campaign if Thurmond decides to run.
May became DeKalb's chief executive when Gov. Nathan Deal appointed him in July 2013 to replace CEO Burrell Ellis, who was elected to a four-year term in 2012. Deal had suspended Ellis after he was indicted, and a jury last year convicted Ellis of perjury and attempted extortion.
Candidates will file to run for office in March, leaving less than two months before the May 24 Democratic primary election.
In DeKalb, where a majority of residents vote for Democratic Party candidates, the primary usually decides the race. The general election is Nov. 8