Hello Dijon, I have some questions

1. When I go to Network -> WAN Settings, I saw eInternet but there is no edit link, I only saw the view link at the action column. What do I do? I inspected and removed the "disabled" code but there's no way to save it when I tick again the "Enabled VLAN ID". In this same page, the VLAN mode available were Maxis Own Build, Maxis-TM, SACOFA, CTS and TNB-Setia Haruman, which is the correct mode?. Did I do anything wrong?

2. It's confirmed that the Archer C5v that was given by Maxis, it can work as a wireless repeater?
Same issues exactly, but my issue was worse, there's no "Save" button at all.

Please advise here, gurus, thank you!

I gave up on getting WDS to work on this router. First thing I did was searching for the WDS option ... this firmware/router doesn't have the "enable WDS" options anywhere in the settings for some reason. Device support WDS bridge though so maybe it's maxis firmware problem. Tried find stock/custom firmware, no avail, probably 'cause this router is only for Maxis/Malaysia so no one bother with it.
Then this guide. I followed and complete all step in this guide still can't get it working. instruction somewhat unclear, different options are shown and probably different firmware version. *shrug
Might be easier to a. just get 30m network cable and do it the old way or maybe buy ~RM100 moddable WDS router instead ...

Hey guys, I successfully set my repeater using WDS on both ISP provided router. May this will useful to you and anyone in future.

If you guys had extra router, you can set it as repeater to cover wifi deadzone in your house. Most router can support wds bridge but that function are locked by ISP firmware. Here i will let you know how to unlock it. I spend lot of days researching on internet. It's easier to connect via ethernet cable but that's not convenient. Wds function are for connecting 2 router wirelessly. I will teach how to unlock only, that's the hard part. You need to watch on youtube how to set you old router as repeater using wds. First, log in your spare router using google chrome browser (important) go to wireless 5ghz page- right click-select inspect (browser function) - find wds and delete "nd"(it may different from other manufacturer). If you had maxis archer c5v like mine, you can directly unlock it by log in using this master password. User name:MaxSysAdm password : Ng88Mxs@2019! . Enable bridge mode in your router. Next, go to your main router you are using go to wireless 5ghz page and right click-inspect - find repeater or wds and delete "nd" or "noshow" that's depend on which router you had. You need to enable wds on all router. Now all your 2.4ghz and 5ghz in your routers can connect to internet. It's took me more than a year and few gave up because no clear instructions on internet. Actually, inspect function in browser people using it to create fake news because you can change word and numbers locally. Hope it's useful to you guys. Now my home had no wifi deadzone and 5ghz full bar any where in my house except bathroom on 3 room because too many wall.
Big thanks to delaciox for show us how to do it and PRSXFENG for root password.