It's not entirely true if you've heard that Thai people tend to eat all day. Generally, they eat three main meals a day just like the rest of the world, but they have a habit of 'gin len' ('snacking') between meals. The whole spectrum of hawker food from savoury 'look chin ping' (grilled meat balls), sweet roti pancake wrapped around sweetened condensed milk with a choice of banana or egg and fried bugs, to freshly-squeezed orange juice, fresh fruits, and frittered bananas are available, at incredibly low prices, virtually everywhere in the city.
Thai people love sharing food. If you go out for lunch or dinner with Thai friends, you are most likely to be asked whether you'd like a single dish or dishes to share. To share or not to share, that is a question entirely up to you. To make things easier, it helps to observe or ask other people in your group what style they're going for. If they've decided on sharing, then you should join in the