Hi Varawut,
I am doing the same thing. Maybe this will help you.
https://www.digi.com/resources/examples-guides/802-15-4-analog-input-with-a-potentiometer
https://www.digi.com/resources/examples-guides/802-15-4-pwm-output-with-an-led
By the way I have successfully did one side xbee standalone.
For example 1 Xbee standalone is connected across and LDR.
The other Xbee is connected to Arduino, which then activates the an LED attached. If you want that I can share the steps.
Thank You