Her real estate career began early when she sold her first house at the age of 16. Phyllis Smithwick Thomas became Vice President of Smithwick Incorporated in 1960 and was Treasurer of Rawick Manufacturing Company, both family-owned businesses. She served as president of the Pine Bluff Realtors Association and was State Director and District Vice President of the Arkansas Real Estate Association.
She was the first woman volunteer president of Pine Bluff Chamber of Commerce and was Director of the Arkansas State Chamber of Commerce 1987-1989. She served on the Board of Trustees of the Economic Development Alliance of Jefferson County from 1995- 2002, Board of Directors for Jefferson County Industrial Foundation, Jefferson Hospital Association, Fifty for the Future, Pines Technical College, The Jefferson County Literacy Council Advisory Board, and the Clean and Beautiful Commission. She was a director of Simmons First Bank Board from 1984-2009, serving on the Executive Committee, CRA Committee, and Senior Loan Committee. She was on the Bank Advisory Board from 2009 until 2013. In 1996, they built Harbor Oaks Golf Club, which is on the Natural State Golf Trail and one of the top 10 public courses in the state. They managed the golf course and restaurant until it sold in 2016.An avid golfer, Phyllis was an active member of the ASGA and AWGA. The AWGA named a trophy and the ASGA host the Phyllis Thomas Pink-Ball in her honor.