Rachel Uchitel's involvement with Celebrity Rehab is causing plenty of drama. Tiger's alleged mistress has checked in ... then out ... and now back in again to Dr. Drew's facility. Now Michael Lohan is saying her involvement with the show is his doing ... and he wants to make sure he gets paid for it.

Lohan claims that he introduced Rachel to her manager, David Weintraub, months ago. At the time of the meeting, Lohan says Weintraub agreed to pay him 25% of whatever projects Rachel takes on.

According to Lohan, Uchitel is earning $500,000 to appear on Celebrity Rehab 4 with Dr. Drew ... and he wants his 25%. However, Lohan says that Weintraub has been ignoring calls from Lohan's attorney Lisa Bloom in the hopes of avoiding any payment.

As for Rachel Uchitel appearing on Lohan's upcoming web show Celebrity House NY, he says she'll make an appearance towards the end of the season.

Reps for VH1's Celebrity Rehab have not been available for comment.