new Death[MAX_PLAYERS]; // put this wherever, under #include or #define 

public OnPlayerDeath(playerid, killerid, reason)
{
    Death[playerid] = 1; // set the variable to 1, which mean, player is dead.
    return 1;
}

public OnPlayerSpawn(playerid)
{
    if(Death[playerid] == 1) // check the player death status
    {
        //if player spawns because of death, do something
    }
    return 1;
}