"What has he done?" Rondo asked, per Bill Doyle of the Worcester Telegram & Gazette.
He also didn't seem to be impressed by the fact Thomas led the Celtics to the Eastern Conference Finals last season.
"This is the Boston Celtics," the New Orleans Pelicans guard added, per Doyle. "This isn't the Phoenix Suns; no disrespect to any other organization, but you don’t hang conference titles. Do we hang going to the conference finals? What do we hang here?"
Thomas spent parts of three seasons with the Celtics, earning All-Star appearances in each of his last two years. After finishing third in the NBA in scoring last season, he came up big in the playoffs despite dealing with the death of his sister.
Despite the effort he gave to the team, he was traded during the offseason in exchange for Kyrie Irving.
The Celtics offered to provide him with a video tribute before his return to Boston on Feb. 11, but Thomas announced Tuesday on Twitter that he didn't want to conflict with Paul Pierce's jersey retirement game.
Meanwhile, Rondo got a video tribute in 2015 when he first returned to face the Celtics after his trade to the Dallas Mavericks. He had spent nine seasons in Boston, earning four All-Star appearances while being a part of the team's last NBA title in 2008.
The 31-year-old clearly thinks there should just be a higher bar for players who get honored in Boston.