Thuy is one of the two main antagonists from the 1989 musical play Miss Saigon (alongside The Engineer).
Thuy first appears after Kim and Chris' wedding, insulting Chris and considering Kim a traitor to her family, but she loves her new husband and that all she cares about. Thuy swears vengeance to them both with a gun unless she refuses to be with Chris anymore. Thuy is the army officer of the Vietnamese soldiers and while he sent them to the Vietnam War, he received the news from The Engineer that something weird was going on Kim's, so he went quickly and while the Engineer left them both alone, Kim confessed that after marriage, Chris and her made a child and named him Tam. That was the reason she couldn't marry Thuy, who just got really mad and attempted to kill Tam with a knife, but after a moment feeling so nervous and thinking she wouldn't know how to do it, she shot at the officer and killed him. The whole nation would go after Kim after this, so she planed to go with her child Tam, The Engineer and Chris' friend John. But Thuy's death wasn't his end for Kim, because usually she was still dreaming of him, after all she killed him. But among all her dreams about him, she had one where he talked about the war and Saigon would lose it finally.