Sources close to the promotion confirmed the news to FloCombat on Sunday. A search for a replacement opponent for Chandler is underway.
Thomson (22-8), a veteran who made his pro debut in 2001, has won two consecutive fights since leaving the UFC and signing with Bellator last summer. He last appeared in December, beating Pablo Villaseca by TKO in the second round. Thomson seemed to be in line for a lightweight title shot against current champion Will Brooks, but opted instead to face Chandler in a fan-friendly bout.
Chandler has won two consecutive fights since losing a trio of bouts to Will Brooks and Eddie Alvarez.
Bellator's May 14 event is headlined by a light heavyweight bout between Phil Davis and "King" Mo Lawal.