Thais are the ultimate snackers. The typical day includes not only a morning meal, lunch and dinner, but there's rarely a day without an afternoon and late night snack. Any of the other foods discussed in this site may be eaten for a snack, especially noodles, but there is also a whole other group of foods that are best categorized as snacks. In restaurants catering to westerners, some of these dishes become appetizers, and it's not even unusual for Thais to order these dishes as part of a large meal.
Oddly, although perhaps not surprisingly, there are several words for snacks in Thai. The term I've used, gup glaem, literally suggests “food to eat with drinks.” These seem to be the most appropriate words to use for many of the most popular northern Thai snacks, given the extreme spiciness of many of these foods. Of course, “drinks” more often than not implies cold beer, or perhaps the Thais' own rice whiskey, typically diluted with cola or soda water.
The other common term for snacks is a-han wahng, which roughly translates to “food for free time,” suggesting that, where Thais are concerned, one's free time is best spent eating.