TP-LINK AC1200 Wireless VDSL / ADSL Modem Router Model: Archer VR400

Purchased in Thailand but now in use in Phnom Penh, Cambodia. Select Region but Cambodia is not listed.

Internet comes via an Ethernet jack on the wall. Set up the modem router as a regular wireless router to share the Internet.

I can't go past the Quick Setup Wizard without Select Region and Time Zone, I choose Thailand and then I can enter the

Advanced> Operation Mode, select the Wireless Router Mode and have set up an Internet connection successfully

Have a Atech 4G USB modem dongle W9600A3G / 4G bud cannot use because I can only choose Thailand's mobile providers.

downloaded the last firmware from TP-LINK website