LAN and guest WirelessLAN on same VLAN possible? (Using Merlin on RT-AC66U)

Hi there

i want to use the guest WLAN and connect it to a specific vlan.
And then i want to configure an ethernet port to also use the same vlan.
So both can communicate with each other.
Is that possible and how?

Detailed Info:
Im using the AC66U as an AP

1. Network (Private Network; Done):
NAS on Port1
My Notebook on normal wireless lan
and the router to the internet.

2. Network (This is what i need to Setup)
Tablet and Smartphones connected over wireless guest1
Phillips HUE...

LAN and guest WirelessLAN on same VLAN possible? (Using Merlin on RT-AC66U)