Critics have questioned whether the former Playboy model's tragic demise is appropriate content for the new production, scheduled to open at London's Royal Opera House later this month (Feb11).
But Thomas, who wrote Anna Nicole with Mark Anthony Turnage, is adamant Smith was an ideal muse for the project.
In a column for Britain's The Times, Thomas writes, "People ask me if she's worthy. What's 'worthy'? And who gets to decide? Everything is a fitting subject for an opera. Every life lived contains glory and tragedy.
"It doesn't matter what you or I thought of her or the choices she made. No one goes to the opera to judge Salome or Carmen. We go to see a wonderful story and to hear it told in an absurdly beautiful medium. Anna Nicole's life is absurdly beautiful...
"I never met her. I don't have the answers. But the questions! The questions are endlessly fascinating and perfect for opera."
Thomas' opera will chronicle Smith's rise to fame, her marriage to aged billionaire oil tycoon J. Howard Marshall and her demise at 39.