NBA legend Paul Pierce's baby mama went back to court in their bitter legal battle … claiming Pierce is playing games when it comes to turning over his bank records ... TMZ has learned.

TMZ obtained court docs filed by Paul's ex, Princess Santiago, and she's claiming he has failed to turn over all of the relevant financial information she's asked for in the case. She claims he has not produced all the pages of his bank statements and did not provide certain information about his trust distributions and assets.

She says Paul failed to produce info on his cannabis company and all data about his Fox Sports 1 income … and she claims he failed to disclose his ownership interest in a commercial property.

Princess says Paul also failed to pay her the $10K he was ordered to pay her so she could hire a forensic accountant to review his finances.

In her motion, Princess is asking for an extra $40K for legal fees and to cough up the $10K for the forensic accountant.

As TMZ first reported back in August, Paul was ordered to pay Princess $8,508 per month in temporary child support for their son, King Rafael Santiago Pierce. The court also ordered Paul to pay $100K toward her legal fees.

The NBA star's ex claimed Paul earned over $200 million while in the NBA. Paul told the court he was not pulling in massive amounts of money like he was during his NBA playing days and wanted any awards he was ordered to pay to reflect that.