My daughter keeps getting caught in the paid sms scams. They keep sending sms at 8bt per message until all of the available credit is used up. I have canceled them already with the *173 number, but Is there any way of blocking them permanently?

In the eService website of AIS there is the possibility of cancelling SMS subscription with fees.

I don't know whether it does more than that *173 code (what does it stand for?).

eService:

https://aiseservice.ais.co.th/eServiceWeb/

(you might need to click "EN" in the upper right, mobile phone must be at hand)

-> Other Services

-> SMS/Preference Cancellation

-> SMS Subscription with Fees

-> To request for a new SMS cancellation by Sender Name Click here.

If nothing helps than I am afraid you to work throgh the customer hotline (1175) with daugthers phone or visit an AIS service center.

*173 is the cancellation service.

OK, so sounds like you look for a "parental lock" to prevent your daughter to subscribe again?

I can not help with that.

Only thing you can check:

new SIMs always contained a lot of such preconfigured service numbers (most stupid stuff like horoscope etc.).

They can be deleted. Clean up the address book.

Apart from that I am clueless how to keep back your daughter to do silly stuff with the phone.