The Monster's Ball star has signed up to reprise his role as a conman who masquerades as Santa, but the follow-up has yet to go into production.
Thornton has now revealed Bad Santa 2 has suffered numerous delays, but is finally due to start filming early next year (14).
He tells Britain's The Observer newspaper, "It's been pretty hard trying to get the script right. We've been through three or four drafts but we're getting real close.
"Then there's the business dealings to sort out, all the stuff I don't understand. But one way or another, the sequel will happen and the idea is to shoot it next year. We know we'll never beat the first film but we'll get as close as we can.''