The wives prepare to wear the uncomfortable European dresses and shoes Anna has instructed them to create for the dinner and performance (“Western People Funny”).

During the dinner, Tuptim sneaks away to meet Lun Tha, who reveals that he has been ordered to return to Burma immediately. They plan to run away together after Tuptim’s performance (“I Have Dreamed”).

In the theater pavilion, Tuptim and the royal dancers and singers present a Siamese version of Harriet Beecher Stowe’s book (“The Small House of Uncle Thomas”). During the presentation, an emboldened Tuptim confronts the King about slavery, but he quickly puts her back in her place. Afterwards, she disappears to meet Lun Tha.

Aside from the outburst from Tuptim, the King and Anna revel in the success of the evening. The British no longer view the King as a barbarian. Anna and the King begin to share their thoughts about relationships between men and women (“Song of the King”). The King expresses a curiosity in Western-style dancing and Anna and the King dance an exuberant polka together (“Shall We Dance?”).

The Kralahome interrupts with news that Tuptim has been found. She is brought in and the King prepares to whip her. Anna, begging him not to punish her this way, calls the King a barbarian. Unable to proceed, the King exits. When Lun Tha is found dead, Anna is devastated and vows to leave Siam.

Over the next few months, the King’s health begins to decline. As Anna and Louis prepare to leave, Lady Thiang brings Anna a letter from the King, who is close to death.

Anna arrives in the King’s study, where the wives, children and priests are holding vigil over the dying King. The King asks Anna to teach the children to be brave and Anna decides to stay (“I Whistle A Happy Tune” Reprise). As the King dies, Prince Chulalongkorn proclaims a new vision for Siam, inspired by Anna’s teachings. The Kralahome, Lady Thiang and Anna kneel by the great King’s side, paying their last respects (“Finale Ultimo”).