So Thiwthit had always been behind the death of Armin and both times it was because he was obsessed with Thada and wanted to take Armin's place in his brother's life.
Clearly, he has always been crazy about Thada. He never did anything to his previous lovers because Thada never loved them, but Armin was different and that's why he wanted him gone.
If his ploy to get rid of Armin worked in their past life, this time he wasn't successful and ended up in prison for his crime. Thada hopes it's going to teach him the consequences of his acts, but I think nothing can be teached to him.
He is losing his mind and I'm not sure prison can really help Thiwthit. At least, he can no longer hurt Thada and Armin.













