Will God hold the one who commits suicide accountable for his intention, and will he be considered an apostate for believing he will die as a disbeliever? What is the ruling on one who commits suicide?

Suicide does not expel one from the faith, nor is it considered disbelief (kufr). Whoever believes that it is, their belief is incorrect. The causes for apostasy from Islam are through belief, speech, action, or omission. However, if a person commits suicide while believing that it is an act of disbelief and is content with that, then they are considered a disbeliever, based on the saying, "The intention of disbelief is disbelief."