Thoughts of suicide are indicative of a psychiatric disorder and should not be regarded as a source of shame. Communicating the truth to others is preferable so that they can better understand mental illness and your personal experiences with it. It is unfortunate that you are compelled to tell lies to your friends, but if that is the case, they are not truly your friends. Indeed, if they are your good friends, it is not nice to psychologically toy with them over such a serious matter.
You could share that you have disturbing thoughts and suffer while depressed; nevertheless, you are not required to give any scary details or future plans.
This is because confiding in someone you trust can help you feel better and less depressed. Suicide is less likely among people who have a loving support system. When you feel overwhelmed and communicate in a way that your friends do not understand, you could be missing out on the opportunity for your friends to be a source of comfort.