Sia Plans to Testify at Upcoming Spousal Support and Custody Hearing

Sia's laid out the witnesses she plans to call at her upcoming spousal support and custody hearing ... and she's listed herself as chief among them.

According to a new filing, Sia says she expects to take the stand at a hearing for approximately 2 hours on issues such as spousal support, custody, visitation, attorney's fees, and more.

Sia also lists her estranged husband, Daniel Bernad, who she expects her lawyers to cross-examine on various issues like custody ... and accountant Tracy Katz, who she says will testify about child support and other financial issues.

As you know ... Sia -- who is being repped by disso queen Laura Wasser -- and Daniel are going through a very messy divorce and custody battle over their son, Somersault.

Daniel claimed Sia's debilitating drug problem posed a problem with parenting effectively ... while Sia fired back by claiming Daniel had been investigated for child pornography.

A judge previously ruled most of the facts in Daniel's filing were old news and shot down his emergency request for full custody of their son ... and subsequently ordered them to go to mediation and try to hammer out a custody agreement.  And if that doesn't work, it looks like they'll hash things out in front of the judge.