Due to the haywire system of tmnut , certain areas will be affected with random ping.
CS does not even know how to handle the problem and how to output the situation to their respective backend.
Usually they'll just ask the backend to reset your port which does not solve the issue.
When it comes to international connection, it requires more communication to check on the issue which will be usually ignored unless there's a high amount of users being affected.
If you're minority, you're out of luck.

Solution.
What we usually deal with lag spike is we get vpn/tunnel services to route & shape the traffic properly.
There're many types of VPN/Tunnel services provider around globally.
What i suggest would be looking into game specifically vpn service such as battleping or wtfast .
They are for games and strictly not for downloading purposes. Prices will be a lot cheaper then a fully tunneling services such as bolehvpn.

Battleping-Easy selection of server (Nearest is the best always select Malaysia) and click connect , that's all.

If you like easy interfaces without the highly customizable functions like walking into a pilot cockpit , i suggest going for battleping. A simple 1-2 clicks brings you straight to what you need.

WTfast- UFO cockpit. They can be fast but if you're not alien or alien literate , you mind end up not moving the ship at all.

WTFast is highly customizable and certain users are able to get better ping rates from wtfast over battleping. But for users who went in and thought that they walked into some alien spacecraft cockpit , you'll end up getting very much worse that you could imagine.

I've tested trial for wtfast once. I couldn't get it to be stable for my ff14.
I went in the advance setting menu and i was stumped by the multi configuration they had and it's not user friendly.
Though quite many of the players i know prefer wtfast over battleping. Which is wierd to me.
Maybe they know alien technology while i don't.

I've tried battleping a few times and it's very stable and user friendly. I'm getting less then 50 ping rate to ff14 with a 4mb screamyx connection. I used the Malaysian server which is in beta stage but it's stable enough.
Without battleping, i get from 200-500 latency that fluctuates depending on dense population or low populated area.
When opening doors or interacting items, i open as fast as japanese players.
Without battleping, even i'm first to interact, a player quite some distance from me could just run up and disrupt me from opening the doors.

https://www.offgamers.com/tools/vpn/battleping


I bought from offgamer. Don't buy from battleping directly using paypal options, it's USD and the price conversion is not cheap.

I usally buy 90days. Battleping have trial for users to try first before buying.
Though i remember that it'll disconnect you after 20-30mins of usage if i'm right.
It should be sufficient enough for you to try out if it's stable for your connection.

Ya. No matter how you rant or complain, it won't help at all. This is a bad route traffic situation.
For example, your game packets/traffic suppose to go through the nearest available route to your destination instead took a longer route.
Example, you are trying to connect to a game server in singapore. Your ISP did not go through from malaysia to singapore. It go through Europe and other region first before coming back to singapore. Of course speed test will show normal because their gateways are established directly towards the speedtest point without hopping through any other gateways. The only condition which you'll fail speedtest miserably is that when your fibre or copper line quality is faulty and fails to transmit data properly. Or you are facing service interuption in your area. That's the only thing that will cause speedtest issue. Other then that , all international connecition speeds are not accurate with speed test.

What does vpn do ?
VPN divert your traffic and make sure that it specifically reached an establish direct connection with the vpn gateway.
Instead of going through europe, now it direct you straight to singapore.
But take note though, all datas went into VPN are viewable by the provider depends on whether he wants to do it or not. He might say that everything is confidential but there's no guarantee that those datas are intact.
Which is why certain games have security game tokens such as ff14. Even they know ur username and password, it still require another separate one time key to enter. And it's also adviseable not to use vpn when you do your online banking.