On my Samsung ( not a Series 9 ) the touchpad is controlled by a function key sequence. On mine if I press [Fn] and [F9] together the touchpad is disabled, and remains so. Check your user guide to see if the Series 9 has a similar key control as the Fn key may be a different one.
If you open <Control Panel> <mouse> is there an option in that applet to disable to touchpad? Again, on my Samsung its <control Panel> <mouse> [Device Settings] tab and click the disable button.
You should also be able to disable it from <control panel> <device manager> under 'Mice and other pointing devices', right click it, - properties - [driver] tab. You will need to be in an Admin account or at Admin level to disable a device.