My experience...
I have a KTC Thai credit cards (3) since 2011.
About a month ago the bank rang, late on a Friday night, and informed me that my wife's credit card (second card holder under me) has been compromised and they spoke to visa international and the card needs to be cancel immediately!!
I immediately hang up thinking it was a scam call and I rang back KTC myself to find out if it was really them or not.
KTB Call center confirmed the story and they strongly suggested that the card needs to be cancelled asap.
So I got them the cancel the card and a replacement card arrived in few days.
Apparently someone in Europe tried or was going to try using it.
I'm very very careful with using my KTC and Krungsri credit cards here in Thailand, as if something goes wrong I won't have the same rights fighting with the bank as if I would have back home with the commonwealth bank of Australia.
Both KTC and Krungsri apps notifications are on and an otp is required for any transactions over 1 Baht. better safe than sorry ????