Michael Jackson's Assistant -- I Paid MJ's Bills in Vegas ... And I W -

Michael Jackson's personal assistant covered a bunch of expenses while the King of Pop was living in Vegas. Now, three years later, he's finally getting around to demanding payment.

Michael Amir Williams filed a creditor's claim with the Michael Jackson Estate, claiming he's still out $28,569.83. Among the items listed -- an $11K power bill, a $13K vehicle lease and almost $1K in phone bills.

As for why he took so long to file the claim, it's a little unclear -- Jacko kicked the bucket back in June 2009 ... and most everyone else filed their claims years ago. In fact, he may have missed the filing deadline by a long shot.

Williams also filed a class action suit against AEG recently ... which AEG didn't really appreciate.