Draw and erase graphics from an image in a picture box using C#

bool draw;

private void Form1_Load(object sender, EventArgs e)
    {
        pictureBox1.Image = new Bitmap("Image.jpg");
        draw = true;
        Thread DataRead = new Thread (Data_Read);
        DataRead.Start();
    }
      public void DataRead()
    {
        //code for data reading//;
         
         if (data_read !=null)
           {
             draw = true;
           }
        else 
           {
             draw = false;
           }         
      }

private void picbox_paint(object sender, PaintEventArgs e)
    {
         if (draw == true)
        {
            e.Graphics.DrawImage(new Bitmap("interface.png"), Convert.ToInt32(x), Convert.ToInt32(w), 16, 16);
            e.Graphics.DrawImage(new Bitmap("interface.png"), Convert.ToInt32(z), Convert.ToInt32(y), 16, 16);
         }
         
        else
        {
          // what should I do in this part?
        }
 e.Dispose(); pictureBox1.invalidate();
    }