Season 1 of Candle in the Sun premiered on May 18, 2019.

Kalin, a famous model, is in a scandalous controversy because she is with a married man but she doesn't care about it, since he told her that he is going to get a divorce. One day, she found an ancient golden hairpin that made her dream of Thiankham, a woman who has the same face as her. She saw all of Thiankham's life and felt angry for her. The hairpin shows its power by bringing her soul to Thiankham's body.

Thiankham, a naive girl, was adopted by Nankham, the hunter of the vassal prince. One day, she was attacked by a tiger and Thewarit, son of the vassal prince, said that he would help her. That made Thiankham feel grateful and respectful towards him. Finally, she became his mistress. Wongduean, who is Thewarit's wife, is so angry. Thiankham tragically dies and vows to be strong and fierce in the next life, so she can get revenge on everyone who treated her badly.