You're lucky to be based in JB/Johor to have found a Unifi IP range that links directly to one of CF's VPN server which is hosted at JBIX. By connecting directly to JBIX, you get to enjoy sub 10ms ping rates to SG within 1-2 hops after that which is good routing strategy.

However TM's Unifi users who are based in different regions(Northern, East Coast, Sabah/Sarawak) do not have this advantage. TM has many concentrators/edge routers spread out in different regions, probably one in every state and this is where the extra ping times is introduced especially during peak utilization season like now during festive Raya/CNY where they become overloaded with traffic.

Here is what I discovered from doing reverse tracert from Equinix/NTT/internal TM servers.
The round trip from Penang alone to JB would probably take up around 10ms-15ms.
The round trip from Cyberjaya to SG is about 10-15ms
The round trip from Sabah/Sarawak ~15-25ms

Example when a undersea cable is launched such as the ASE, it claims to achieve ~60-65ms from Changi-> Tokyo.So if I was to ping a connection from KL to Tokyo, it would roughly be 5-7ms(KL-Cyberjaya)+10-12ms(Cyberjaya-SG)+60-65ms(Changi-Tokyo)=~80-85ms

It gets even higher during peak hours/festive periods.

Different concentrators/edge routers in different regions will get different range of IP addresses for TM Unifi.
That is how they separate your IPs by location.I've read some of the users attempting to follow your advise and rebooted their modems over 10X and still not getting the 175.140.x.x range suggested is because they might not be connected to the same concentrator as you in different regions.

The reason why you might get as high as 40ms to SG even when you're so closed to the island already is because probably of TM's bad routing. It is probably making a BIG U-Turn round trip from JB-TM Cybejaya NOC-SG with different IP range getting different routing results.

Why certain Unifi users are now getting very bad connections is because the concentrators which they are now connected to are probably very CONGESTED now. They are believed to be located in northern region(Kedah/Penang/Perak) or East Coast(Kelantan/Terengganu) where all the balik kampung activities are now residing. I'm aware of this because the reverse tracert results shows that the ping rates from SG(datacentre)-Cyberjaya(NOC gateway) seem to be fine which only peaks around 10-12ms.

Trust me, similar IP blocks if you are in JB while I'm in Klang Valley but the routing is slightly different because of distance and area specific concentrators/edge routers are different.I would never get to enjoy sub <10ms to Singapore even if I connect to the CF server based in JBIX.

With TM's mess when it comes to routing, you might get lucky with certain ip ranges with less hops(shortcuts) but still circuit distance still plays quite role when it comes to latency.