Which software are you using?
Carbide Create allows as thin as 0.1mm:
For doing this, see:
and:
That said, why?
They’re easily done by hand:
but on a CNC require a minimum of 3 setups:
- cut parts to size/length, machine any internal features
- clamp four boards on the machine, two flat, two vertical and cut joints at two corners
- rotate boards (maintaining the correct orientation) and cut the other two corners
Far easier to use a joint such as a full-blind miter box-joint:
which allows cutting a ready for joinery part in a single operation.