I have heard rumor occasionally in tibet there existed or possibly still exist those that would put themselves in a particular meditative state in which the bodily processes were almost stopped. One remained alive however but not appearing alive.
The person could be brought back I think only by spiritual means. And once brought back they then did not live for very long after.
The story I have heard had the chinese coming upon some of these in a cave somewhere, not knowing what they were just threw them out, thinking them dead bodies mumified perhaps.
It was not suicide though as they remained alive, just so slow were the processes of body they lived many centuries but did not awaken. From that they normally just died, eventually.
That story reminded me of that. Suicide as means no current buddhist school of any recognized lineage supports that.
"This order considers that progress can be achieved more rapidly during a single month of self-transformation through terrifying conditions in rough terrain and in "the abode of harmful forces" than through meditating for a period of three years in towns and monasteries"....Takpo Tashi Namgyal.