Using internet and services like TripAdvisor are something we all do to find a cheap and good restaurant. However there are other methods that function better. In large cities the best priced food is often at 1st or 2nd floor. Look where the locals goes, then the experience will be best. TripAdvisor does only give you tourist places that all are more or less expensive. In Bangkok some days ago Emeric and I did eat lunch for only 1,5 US$ each. Good food and good service.