((((((((ExiExi))))))))))
I'm sorry you're in so much pain. When I was suicidal, there was no stopping those kinds of thoughts coming into my head, but I did realize that I didn't really have to pay attention to them either. Try to distract yourself as much as you can. Engage your mind in anything else and keep reminding yourself that those thoughts aren't coming from you, they're coming from the depression.
The other thing that really helped for me was the word "NO." Every time I had a thought like that, I would think "NO." I would trace the letters in my mind, I would think about how it would sound spoken by the various people I've known or actors with distinct voices. I would think about all the words I know for "no" in other languages. If I was really stuck, I would just repeat it to myself over and over until the suicidal thinking subsided. I don't know why, but it helped a lot.
Good luck. I hope you find a way to get rid of these kinds of thoughts for good.