Ok @js, you could change your commands.json to this:
[
{"trigger":"Monitor","command":"/root/monitor.sh","ground":"background","voice":"Monitor","allowParams": "true"}
]
And put this in your /root/monitor.sh script:
#!/bin/bash
if [ "$1" = "on" ] ; then
echo Turning it on
vcgencmd display_power 1
fi
if [ "$1" = "off" ] ; then
echo Turning it off
vcgencmd display_power 0
fi
And say this to Alexa or Google Assistant:
ask TRIGGERcmd to run monitor with parameter on
Or use the TRIGGERcmd Smart Home Alexa skill or the SmartThings integration with Google Assistant, and say this:
turn on monitor