Audio/visual unsynchronized: The violins in the orchestra at the anniversary celebration are obviously not in sync with the music they are "playing".
Anachronisms: Daisy Bell ("A Bicycle Built for Two") was published by Harry Dacre in 1892. This movie is set in the 1860s.
Audio/visual unsynchronized: When Anna and King Mongkut first dance, the song being heard has full instrumentation (horns, woodwinds, etc.). But all the views of the musicians entering the ballroom and playing show only string instruments.
Factual errors: The Thai language used between the King and his prime minister is not royal Thai language, but everyday Thai language. Everyday Thai language is never used to speak to a member of the royal family, especially the King.
Continuity: After the fight between Prince Chulalongkorn and Louis, King Mongkut goes and investigates the reason for the fight; he sees Louis writing lines and his son just standing there. Chulalongkorn is on Anna's right while Louis is on her left. Later, when Louis is finished writing his lines he is on her right and the prince is on her left.
Anachronisms: In the scene where Anna first meets the King, the French ambassadors are delivering "a present from the King of France" (in French in the dialogue). In the 1860's France did not have a king any longer: its leader Napoleon III had the title of "Emperor".
Continuity: The King's favorite daughter, Princess Fa-Ying (Melissa Campbell), dies of cholera. Yet she appears after her death with the rest of the royal family briefly aboard the royal steamboat as the King attempts to take the royal family to safety from the insurgents marching toward the palace. Then, after the ship lands, the King and family pray at a shrine to Buddha, and Princess Fa-Ying is again seen with the rest of the children as the insurgents approach from the other side of the river.
Factual errors: Louis asks Anna, "Doesn't "Chang See Khao" mean White Elephant?" While "Chang See Khao" does literally translate into "white elephant", the correct term is "Chang Peuak."