Cultural difference or just plain rude?

The other day, my boss was driving my co-worker, Jesse, and I to our adult business-English classes in the next city over, as he does every Monday-Thursday. During this ride, I decided to bring up my departure, which is quickly nearing. I started like this,

"Mr. Lee, when should I start looking for a ticket to go back to the U.S.?"

In response, he burst out laughing and said "Oh, that is a really awkward question! A Korean man who doesn't know American culture would think you are being rude!"

I was a bit surprised and told him that I was not trying to be rude, just wondering when I should get my departure ticket for, since I will be leaving soon. He told me HE understood, but another Korean man might think I was saying "I want to get out of here!" Anyway, he went on to say that if I ever return to Korea, I should contact him because International friendships are important. THEN, out of nowhere (or maybe because we had just talked about friendships and he felt comfortable enough to do this?), he said:

"You know, Dana, you have been gaining and losing weight a lot recently. That is what happens when people take drugs."

Jesse then piped in with, "Now THAT is an awkward question!"

I was a bit shocked and flustered by that and started laughing and then going on about how I haven't noticed any significant weight gain or loss but who knows because in winter I don't exercise as much because it's so cold outside so it's possible I've gained and lost some weight but the scale has never showed more than a 5 pound difference, blah, blah, blah. I then realized that possibly more important than his opinion on my weight changes was his suggestion that I take drugs. I switched tracks and said, "Mr. Lee, do you think I take drugs?!"

He then started laughing and said "That never came to my mind, I was just surprised at how much weight you gained a few weeks ago. I know you don't take drugs but if you see on TV, when the actors lose and gain weight it is because they are on drugs." Then he went on to say that maybe it was because of how I was dressing (lots of layers seeing as its Winter!).

When I got to my adult (all male) class, I brought that up and asked if that was normal in Korea. They all had a good laugh, first, and then said that a man should never say that to a women in Korea, BUT if it's your boss, well then..what can you do? So apparently comments on your weight are OK as long as they are coming from your employer. Good to know.