Bungee Jumping of their own- It's a standard movie, guy falls in love with girl kind of thing then the girl dies. She gets reincarnated as a boy. The ML finds this guy (it's his student), realizes it's his soulmate from way back and tells him and they decide to run away together. But they decide to run away together so that they can commit suicide and hopefully find each other in the next life. Instead of living as a gay couple, they would rather die.
it's Thai but also, Mook Liam Petch- The main antagonist is gay, and is obsessively in love with his best friend. He tries to sabotage every straight relationship the main lead has, and treats his gay lovers poorly. It was a while ago when I saw it, I think he might have even killed one of his lovers for getting in the way of his plans with his straight best friend but I don't know for sure.