Good day @keigoleung,
Welcome to TPG Community!
I have run some remote line test and was not able to detect any issues or fault on the line. I can see that your modem is receiving a good sync speed with 4175 Kbps Downstream and 1020 Kbps Upstream rate given that you are about 3.69 Km away from the local exchange.
Were you using a wireless connection? Have you tried an isolation test by disconnecting all of your devices on the network and leaving only 1 device connected? Are you able to try running some test via direct connection to eliminate the possible wireless signal issue?
I have tested in 1 single device connected with wire connect, and have done a power cycle on the modem/router.
The speed back to normal on sunday later in afternoon. and it is slow again today after i come back home.
the speed now is only 0.7