Hi Karin
I have tried the whole different phone thing --International roaming,public phones and finally settled on the Sim card from whatever country I am in.
I have not long come back from Bali and spent about $20 AUD on local phonecalls ,calls home to Aus and many many text messages--that was over a 15 day stay too. Will definately be taking the same option when I go back to Thailand.
I keep my old unlocked phone as a spare for holidays save all the numbers to the handset then its ready to go when i arrive at my destination.
Cheers laurs