When I was in Bangkok last week I used my mobile phone to call back to the USA with my True Sim card , you can get 2 rates , 1 baht a minute and 3 baht a minute ,
The 1 baht a minute was usable but not good , but the 3 baht a minute was amazing , it was as if they were in the next room .
I believe it was 006 then 1 and USA number for the 3 baht a minute calling ,
Is there another way to get the high quality call for less ?

and on the USA side calling Thailand , I use callmuangthai.com , its cheap , 1-2 cents a minute but the quality is bad just like the cheaper True sim.
you dial an access number and if your phone number is registered with them you do not need to enter a PIN code, I have my USA "dumb" mobile phone and home phone registered and the thai numbers I call on speed dial

Is there another service that I can use that will get me "next door" quality. and work on my "dumb" phone ?

I assume these are both VOIP , and there must be many grades of quality available.

I am calling Thai Mobile phones and landlines so it needs to be phone to phone and not VOIP computer to computer.

Thanks for your ideas