The 21-year-old gave the answer to a question on Twitter that he thought was meant for him, but actually appears to have been directed at Scotland under-21s team-mate Oliver McBurnie, who’d responded to a rant by Thomas.
The fan asked “when you signing for Rangers mate”, to which Thomas replied “never in a million years”.
The answer made the wide player very popular with Celtic supporters on the social media platform, as the tweet was liked over 1,000 times.
Thomas signed for Kilmarnock earlier this summer after being allowed to leave Motherwell.
He’d been on the books at Fir Park for seven years having initially been a product of Celtic’s academy.