If your're in Thailand and have an AIS/One2Call phone, you can take advantage of FREE international calls.
This service is available only to 5 destinations - USA/China/Hong Kong/Singapore and Canada.
There is no charge for international call - its FREE but you will be charge 2/baht a minute by AIS.
Simple dial *490049 and hit the call button then wait for voice prompts to enter the destination number you wanna call.
Fuss free .. worth a try !