I don't think you can do that. To replace Maxis home fibre router, you need a router that supports VLAN tagging.

From what I find on the web, Xiaomi Router 3 dont have VLAN tagging in its specification. (I might be wrong)

I got my router replaced with a Asus RT-AC66U. Asus has build in firmware that support Maxis Fibre. All I need to do is to select Maxis Fibre and it configure itself.

That can be done, but then whats the purpose of Xiaomi router then? The whole main point of replacing is because that Thomson router sux.

Your Xiaomi router will only function as an Access Point. And you wont get the full bandwidth of the Xiaomi router because you have a bottle neck which is the Thomson router.

No no, please don't get me wrong there. I did not say Thomson router will bottleneck Maxis Fibre. Maxis is only providing 10Mbps, there is no way it will be bottleneck the low speed of 10Mbps. What I am referring to is the Intranet speed. I got all those setup years back. Thomson router only provides you with a slow Intranet speed even when you connect via LAN. The Xiaomi router has a Gigabit port while the Thomson router only has a 10/100Mbps Wired. Above that, you cant connect a personal cloud on the router. There are many more disadvantage of the router on terms of features.

The Wifi is really bad on those routers. If you are just a normal user and doing things like gaming, web surfing, etc, then there is no issues with it. If you like to setup a WD cloud, a personal server, storage, having file transfer within your home or office, then you will feel the pain cause the transfer rate of the router is horrible.

Sorry for the late reply. Yes, still can. But if you want to use the phone, you need to use the Thomson router. Which mean you will use Asus router for your wifi and all the data transfer and Thomson router for phone. The function of the Thomson router here is only for phone.

But I have remove the Thomson router totally because I dont need the phone as all calls goes to my cell phone.

You can refer to the link below as an example. There is a Asus treat here that will guide you to install. Need to search the forum a bit.

https://forum.lowyat.net/topic/2384890