I just had my first ever Siam Terrace carry out box lunch special, and I am really impressed. It's a shame they don't advertise it better, because it's a really great deal and very convenient.
It's for carry out only, and $8.50 gets you an egg roll, salad, and your choice of Thai fried rice, Spicy fried rice, Pad See You, or Red Curry. You can get the entrees with either chicken or vegetable. That said, I got a Pad Thai with tofu and vegetables today and it only cost me an extra $2. They don't seem to be terribly picky about substitutions.
The portions were smaller than if you eat in, but I was still stuffed. It comes in a really nice little partitioned tray that's sturdy enough to be reused (free tupperware - score!). They will also deliver if you order 2 or more of the boxed lunches.