During the Vietnam war, all the ethnic Chinese from Cambodia and Vietnam took off. First, they were not natives to the countries so did not feel the urge to stay and fight. Second reason was that it required money and resources (still does, today, in Syria) to finance arrangements to get onto one of the junk boats that allowed you to flee in the first place. Most of those with resources were the Chinese, not the locals.

Because of these two reasons, most of the people who managed to flee and making use of the asylum offered by Australia, US, UK, France, Canada in the Vietnam war and Pol Pot regime were ethnic Chinese. Today these ethnic Chinese are scattered in these countries – Australia, US, UK, France, Canada, many are second generation born there now, and their parents went there by way of Cambodia and Vietnam but they are 100% of Chinese descent.

Today there are almost 40 million ethnic Chinese in Southeast Asia. But there are very few in Vietnam and hardly any in Cambodia.

Second, the people who opened these noodles shops are actual Teochew people who fled to the US by way of Cambodia and Vietnam during the war. They are not Cambodians. I know because my family is one of them.