Sisqo -- Let Me See That 'Thong Song' Money! And There's a Ton of It

Sisqo’s not done getting paid for his biggest hit “Thong Song” … he’s fired off another lawsuit, this time against the company he says jacked more than half a million dollars of his royalties.

Sisqo says he hired 27 Red Music to collect royalties from various music publishing companies. 27 Red was supposed to get funds for all his music released between 1996 and 2005 ... which, of course, includes the '99 mega hit.

Sisqo says the company collected alright ... but failed to hand over $600,000 to him!

He wants all that dough, plus $3 million in punitive damages.