Can you point to the exact place in the bible where it says suicide is a sin? Yeah people dance around the "thou shalt not kill" but really if killing in war doesn't count I'm sure killing yourself doesn't.
I can however find Biblical evidence that suicide and assisted suicide is okay.
Judges 9:54 Then he called hastily unto the young man his armourbearer, and said unto him, Draw thy sword, and slay me, that men say not of me, A women slew him. And his young man thrust him through, and he died.
Judges 16 29-30
And Samson took hold of the two middle pillars upon which the house stood, and on which it was borne up, of the one with his right hand, and of the other with his left. And Samson said, Let me die with the Philistines. And he bowed himself with all his might; and the house fell upon the lords, and upon all the people that were therein. So the dead which he slew at his death were more than they which he slew in his life.
Even Jesus committed suicide
John
10:17 Therefore doth my Father love me, because I lay down my life, that I might take it again.
10:18 No man taketh it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again. This commandment have I received of my Father.
And according to Revelation, if God doesn't want us to kill ourselves, we couldn't.
9:6 And in those days shall men seek death, and shall not find it; and shall desire to die, and death shall flee from them.
The not committing suicide was developed by the Catholic church so that serfs wouldn't kill themselves and go to heaven rather than slaving for their masters.