Having been released from his contract at the Kangaroos, Thomas joked that Simpkin had forced him out of the club.
"The kid's so talented and he's knocked me off my perch and put me out of a job, but it's good. I'm super proud … to see his development over the last 12 months," Thomas said.
"I hope he can have a long career and do well. It's going to be good to see Jy wearing the No.12."