Try checking the text-to-speech feature on any other application and check if it's giving the same results for the word "THE." Also, you can check the pronunciation of the word "THE" while changing the language settings.
Also, please check for any gaps between the letters (It should be THE and not T H E).
If the issue persists, could you tell us if it's a file-specific issue or not?
To know more about Text-to-speech, refer to this article: -