If you are having thoughts of suicide, please call Lifeline at 13 11 14 (in Australia) or one of the international suicide crisis lines from this Wikipedia page.
If you come to me for help and show signs of a serious mental illness or suicidal thoughts, I will encourage you to see a mental health specialist and I will write you a referral. It would be incompatible with my ethics to work with clients who are in danger of harming themselves or others. If, after a review by a mental health professional, it is determined (in writing) that coaching would be a helpful supplement to other treatment, then I will gladly work with you.