I bought a phone card yesterday and was a bit sceptical at first, but thought "what the hell !!"
It's called a "Thai Call" phone card, it's for £20 and you get another £5 free. With it you get 1,500 minutes to Thai mobile phones (2,800+ for Thai landlines) and this works out to be 25 hours. The card actually cost me £11.50, so that works out at just under 0.77 pence per minute and you have 90 days in which to use the credit (3 months).
You have the option of dialing a 0800 (freephone) number, a 0845 (low-call) number or else a 0207 (Inner London) number.
I have now used it twice and it appears to be everything it says
as I've checked my phone bill online and there's no record of the call (i.e. genuine 0800 number) plus I kept a check on the length of my first call and when I made my second call, the time left quoted was as expected.
Happy days !!