I may be wrong, but IMO this might be related to the type of connection.
I do not have any access to the internet, except when I am in a WiFi hotspot where I have the password.
I have a pay as you go on my phone with TrueMove, which I top up when I get below 50 baht. It only enables phone calls and SMS.
Any time I get an SMS in Thai, I automatically delete. Speak English if you want to talk to me.
I have never had money deducted from any of my accounts, in the way the OP describes.