The public prosecutor wants to bring charges in connection with a waiter Liam PayneThe dead man admits he did cocaine with the singer… but insists he received no money and is NOT a drug dealer.

Braian Paiz told us in our upcoming documentary “TMZ Investigates: Liam Payne: Who’s to Blame?” – airing Monday night at 8:00 p.m. ET on FOX – He celebrated with Liam in the singer’s hotel room in Buenos Aires.

Paiz says they drank whiskey and used the cocaine he brought to the hotel. He says they did it twice…the second time just two days before Liam’s fatal fall from the hotel balcony.

Braian says he saw drugs scattered everywhere…along with the Dove soap box and aluminum foil that were widely seen in photos following Liam’s death.

Braian says he never accepted any money from the singer … and claims he even turned down Payne’s Rolex watch when the star offered it as payment.

There’s a gift he accepted from Liam, says Paiz… Watch the clip to find out what souvenir he received.

Paiz is one of five men Prosecutors are investigating Liam’s death.

us too interviewed Liam’s close friend Roger Nores– who the prosecution accuses of abandoning Liam and supplying him with drugs – and eyewitness Bret Watson …who saw Liam fall to his death.