Buns like these can be purchased all over Bangkok. They are of Chinese Origin, but as I have never been to China, I have little point of reference. I will say this: these are the best I've had in Thailand. I've purchased them in Chinatown, but never with great success. Today, two were purchased. The black bean version was consumed before the camera could be produced. Highly recommended.
Here's the other offering: The exterior was nice and flaky, while the insides were sweet, but of uncertain origin. The woman said some kind of bean; Maybe mung bean (thua ngok), but I'm not so sure. Any ideas?