Try Pam Real Thai food, it's on 49th Street just west of 9th Avenue. Really good thai food and friendly service, far more unique choices than typical NYC thai restaurants. Cash only, under $20 per person.

I second the Burger Joint recommendation, inside the Parker Meridien (57th St between 7th & 6th Ave). It gets pretty crowded around normal mealtimes, especially on the weekend; it's a much better spot when you just want a mid-afternoon snack. It's a small counter with casual seating for around 25 people - it's tiny, and if it's busy, you'll get oogled by people waiting to get a seat while you eat. Around $10 per person, it's a great burger.