Hi toastedmalow,
As with everywhere the price of food and drinks varies enormously. Much depends on where you are.
You can eat very, very cheaply at some Thai places, but wine does tend to be expensive.
We've never ben able to find any "local" wine that is to our taste, but some Australian wines appear to be reasonable value (the dry sparkly stuff is great with Thai food).
Beer can also vary enormously - in bars (approx - this can vary)
Chang - 60bht
Leo - 70bht
Singha - 70bht
Heineken - 100bht
To get an idea of prices (food and wine) in a good restaurant try
http://www.blueelephant.com/bangkok/index.html
There are some links on the LH to their munu and drinks lists, which include prices.
For a meal in an ordinary (I use the word loosely) Thai restaurant, such as Suda off Sukhumvit in Bangkok (thoroughly recommended), expect £3 to £5 for a good full meal.
For an intermediate restaurant such as Cabbages and Condoms, a set menu will be from about £10.
This is a rough guide only, I hope that it helps.
Peter