The league made the announcement on Wednesday prior to the teams tipping off for Game 5 in Boston. The Eastern Conference second-round series is tied at two victories apiece.
Sunday's altercation was posted on Instagram by a fan at the Verizon Center. In the video, Thomas can be seen directing a profane remark at the fan in question.
Thomas pointed at the fan and responded with, "I will (expletive) you up, and you know that."