In Eastern Asia: China, Korea, Taiwan and Japan, peoples means of expressing affection are different. What's considered culturally appropriate is different. Public displays of affection are not common, but it depends on the kind of affection and to whom it is given to.
Affection between couples
In the States I think it's pretty common for couples to hold hands, hug and even occasionally kiss in public. In Europe it's common for friends to exchange kisses on the cheek and public displays of affection between couples are even more relaxed than in the States. In Asia public displays of affection between couples would most likely get some stares and looks.
It is uncommon, but it may be getting more common and more relaxed due to the spread of media. So if you find an Asian girlfriend or boyfriend don't be surprised if they won't give you a hug in public. And you may even get the cultural feeling that it's inappropriate before you ever do so.
Same sex affection
What is common may be what you find rather strange or perhaps homosexual at first sight. It's common for girlfriends to hold hands or lock at the elbow and walk together. They are not lesbians they are just friends. Also it's not only between the girls. Boys can also be more affectionate to one another and it doesn't mean that they are gay.
In the classroom
If you're teaching young children in a kindergarten you may find that they can be quite affectionate. Many will want to jump on you or give you hugs. If you ever taught in the States then you would know that it's very different. It's often not a good idea to touch students as you might get sued or something. So teaching in Asia can be rather refreshing as these mores are different.
And it could extend beyond the early years of kindergarteners. I taught a high school class in Taiwan to mostly girls and one day I even got a kiss on the cheek from a student in the classroom. I think her friends dared her to do it. It was pretty funny and I'd say that was more of an anomaly though.
I'd also say that peoples concept of personal space is different too.