Soi Nana specializes in yatai-style Thai cooking, offering a good selection of regional dishes from around the country in addition to popular standards. Flavors and levels of spiciness are similar to what you might find in Thailand, as is the bare-bones noodle-shop decor. Prices are quite reasonable, starting at around Y1000 for a quick teishoku-style meal.
This book will introduce you to more than twenty of Japan's favorite specialty foods that are less well known abroad, along with a guide to the best places in Tokyo to try them and expert tips on what to order. From Bento.com.