Sorry, there is no such thing as a painless suicide.
Suicide is an extremely painful process. Your body wants to
live, so it will resist death.
Pain is our body way of self defense. Your brain will release
chemicals to induce the self defense mechanism.
If u are considering the pain of dying, then it certainly means
the pain you experience in living is not big enough.
If your life is horrible, why don't you make it better ?
Laziness is no excuse.
To die painless death, it must happen when your brain is not
expecting it. That is no suicide.
Thats how the slaughter house kill cows. It's call humane
slaughter. Google it.