Respected Sir / Ma'am,
Going through so many scriptures has not helped me yet in my quest for the question that in this cycle of Birth and death , is " Death" an event pre-planned by the Supreme or it may occur due to man’s own negligence? Can a man end up one’s life even when his end is not near? If so , then leaving one’s physical body specially when the end is not near is against God’s will/Law .Is Death not in the hands of God?Why is he Supreme then?
The questions you ask are the "big" questions of life, aren’t they? Each of us should therefore approach such questions with the humility and perspective not unlike a scientist who realizes the vastness of time, space, matter and energy. We must not presume to comprehend something so beyond the human scale, at least not without the kind of dedication that a great scientist gives to his education and to his craft.
For yogis, that training goes beyond studying scripture but studying the scripture of our soul, which is eternal and all knowing. The intellect is inadequate to comprehend time and space and eternity on the scale far grander than that of one ego and one human life.
Nonetheless, I will share with you some thoughts taken from the teachings of Paramhansa Yogananda. Yoganandaji teaches that in manifesting Himself through the creation, God submits the creation to the laws of cause and effect (the law of karma). The corollary to the law of karma is the necessary one of reincarnation.
Life and death are not whimsical or arbitrary, nor yet dictated by a heavenly dictator. To even state that death is due to "negligence" is to color the event we call death with a judgment that it is a misfortune. Why say this? Everything in creation is born, lives, and dies. Why bother to call it anything but what it is: another change of form by which energy (and consciousness) experience.
People DO commit suicide and hence take their own lives but no guru or savior endorses suicide. God allows the law to rule this universe because he gives the creation his "only begotten son" which is to say a piece of God’s own intelligence and impulse and power to create to every atom and to every human.
It is still all His dream but those in the dream do not know yet, until, acquiring human form and seeking the truth, we awaken to the dream of the cosmic Dreamer.
It is a conundrum and an answerable riddle to ask "Who dictates the time and place of death." If I live a dissolute and unhealthy life I may shorten my natural or otherwise (theoritically) predictable lifespan. I may die in a traffic accident, also, at a young age but just because I do not know why I died so young, doesn’t mean there wasn’t a reason and that my own past actions are the source of that reason. The problem is that most of us simply do not yet understand.
I may not know how a cell phone or rocketship works, or an electron microscope but that doesn’t mean they don’t work. Gravity worked the same before its discovery as after. Only as we advance in divine consciousness do we begin to see the subtle workings of the law of karma.
So, yes, God is "supreme" but he has allowed the laws of creation to operate, as He is the creator of those self-same laws. As we awaken to our soul’s power we can mitigate past karma more easily and God’s grace and love begin to direct our life more than past karma. So God’s love is above his own law, but love is also a law unto itself: a higher octave of natural law, you might say.
Just as a wise parent can step into his child’s life and rescue him out of love in the nick of time, but a father will not pay off the debts of his adult son if the son is not willing to change his evil ways.
I hope this is somewhat helpful for a difficult question.