Noodle soup is the most basic food in the Thai culture and can be consumed as a breakfast, a lunch, or a dinner. The ingredients are varied and can partially be chosen by the consumer. One type of noodles--usually rice noodles--is to be chosen; the wide rice noodles are the hardest to manage with the chopsticks, so take care. Fish or meatballs can be selected from a wide range, and you should be aware that part of those is prepared with the addition of ground insects. Some places will add some tiny omelettes and chopped green onions and dried-out chillies will always be sprinkled on top of everything. If that is not nutritious enough for you, all the places offer liver chops to be added.
Thais usually add chillis till the noodles get a pink hue, but you should be careful and not mimic that action till you are sure you can stand the fierce local mutations. To avoid ‘losing face’ in front of the locals by not adding chilli, you can add lemon juice from the fresh lemons always present on the tables and a few mint leaves placed near them. This spicing is typical of certain zones and will transform you in the eyes of the many local watchers into a well-travelled Farang without burning your tastebuds.
The proper way of eating the soup is to pick up the solid bit with the chopsticks and the liquid with the short and deep oriental spoon. You can enjoy the experience everywhere; even touristy Khaosan Road hosts at least to small restaurants, one at each end (towards the palace at the western end and away from the palace at the eastern one). The regular price is twenty baht or less.