I’ve finally got back to my house today and made some tests with new Tenda’s separated modem and N600 router I installed just before leaving Bangkok hoping to see some good results. Unfortunately, I still experienced lag and delay sometimes although it could be very fast and responsive for most of the time.
So I downloaded WiFi Channel Scanner and found that my auto mapped channel is commonly used around my house. No wonder why I still have occasional lag even now. So make sure to check surrounding’s WiFi Channel signals and setup a unique one to avoid channel interference.