Vonage Voip Great To Usa Mixed In Thailand - Why?

[Sam125]

I use voange on a 2mb TTT plan in a rural area of Korat.

I usually call the US very early in the morning and get clear calls (for $25 per month)

Yesterday I added their Asian package (for another $10 per month) which includes Thailand.

When I call mobile phones in Thailand during the daytime (as an international call usiing 011-66 drop the zero then the Thai number) I usually have a clear connection. However, when a regular telephone (non-cell) I get mostly calls with lots of static.

I wonder why I am getting mixed results and what if anything I need to do to improve my calls within Thailand?