Thai don't say good morning or won't ask soon how you are doing. They choose a comprehensive greeting that is as Thai as it can be. They literally say: Have you already eaten rice? Yet when they say 'no' they do not immediately assume that something is seriously wrong. In the Netherlands you also hope that after 'how is it going' someone doesn't start telling you how traumatic his life is developing.
However, this 'have you already eaten rice' greeting says a lot about the Thai way of life. It is about food, always. You can eat everywhere, there is food everywhere, and if you look over someone's shoulder in the bus or the taxi boat (we are taller) then it is probably about eating on his or her mobile phone. Because a meal without rice is not a meal, rice equals food. Well, noodles also count as a meal, but rather as an alternative for the mother meal rice.
The Thai 'have you already eaten rice' question is old, officially it has only been valid since the 1940s that 'sawasdee' is also a legal greeting. Also in China, Singapore, Vietnam, Cambodia and the Philippines, interested friends are greeted with similar eating questions.