Had some time to kill today, so I made a photoguide of the often-unseen food court on the first floor of the Bangkok airport..
Its on the FIRST floor--- same level as where you'd get the public taxis...
The entrance is beside door #5..
See the photoguide for what it looks like and how it functions.
As to prices, You can get a basic Thai style meal, complete with drink for around B120 to B150 or so.. It's indoors and air-conditioned and offers take-away/to-go service as well..
It's primary clientel are airport/airline employees, but is open to all..
Bangkok Airport Food Court Photoguide: