About to go to Thailand soon on my DTV and will work a bit while there. My question is to those already in LOS with DTV. I will be spending around 4 hours a week or more on phone calls to and from Australia with work and I was wondering what do people do in this situation to reduce their phone bill? As I definitely need to make these phone calls and also need some data, the only option I know of so far to do this is using international roaming on my Aus provider, but it will cost me $5 per day, albeit tax deductible. I know I can get a Thai sim card, but I believe they wont cover me for my international phone calls and will only include data. Any suggestions in how to avoid $5 per day international roaming so I can make the required international phone calls? TIA

Update: I forgot to mention that some of the people l call don't have access to wifi calling, so l am not talking about making calls via Skype etc.