I was also just through Narita in August, and if your layover is in Terminal 2 (United, ANA), then the restaurant options are all open in the main Terminal 2, but opening hours are an issue. Lots of them close early evening. That leaves the food court, which has a few good restaurants (including the not bad Jai Thai restaurant), but there is a closing time there too, so not sure when your layover is.
If you are traveling business class on United, ANA, or star alliance, the ANA lounge is open (great ramen noodle bar and food), but not on arrival, only on departure, so if you are departing to Thailand on star alliance top tier this is a great option. The United Club is still closed at T2 Narita.