When a Thai friend came to visit she dialed 1234 before a mobile number. When my bill arrived it looked like a had been charge about a third of the normal price. Can anyone explain what this service is?

I think its a service from True

I recall TT&T offering this service a few years ago. Since I never use my landline for in-country calls that aren't local, I couldn't say if it the offer was still valid or not.

Works on TOT lines for mobile and long distance calls. Reduces the cost by an average of 1/3rd

But have always been under the impression that if you use it on a local call you get charged at long distance rate instead of 3 baht per call. But if your local call is under 2 minutes then using 1234 for that could save money as well.