Just as Thai people call out to a friend or stranger passing by Where are you going?, they greet friends and acquaintances with the phrase kin khao roo yang, particularly if they themselves are eating. Roo yang literally means "or yet". Kin means eat, but it's rarely used alone; it is often paired, as here, with khao, rice. After all, rice is the staff and stuff of life in Asia, and if you're really eating, you're eating rice. Another common pairing with kin is len, which literally means play. Kin len, then, means to "play eat" or snack, and as I've discussed briefly elsewhere, the Thai are inveterate snackers, and Thailand, as you'll know if you've been there, is full of things to snack on. So very often when Thai people see their friends they are, in fact, eating.
Just as, when we ask How are you?, we expect a noncommital Fine thanks, the socially acceptable answer to kin khao ruu yang is kin leow, I already ate. To reply yang, not yet, would force the enquirer to offer you food, for it would be impolite in the extreme to leave someone hungry, especially if you yourself are eating. Even if you reply that you've eaten, people will often attempt to ply you with food anyway, at which point you can either gracefully give in and take some, or turn it down two, or even three, times before they stop offering.
This, coupled with the Buddhist ethic of compassion, makes Thailand a good place to be a beggar. I have never seen anyone who needed it be denied food there; even the most humble noodle shop will give a clochard a bowl of soup, thereby gaining a little merit for themselves as they provide sustenance for the needy.