Thalassemia is a blood disease found most common among Cantonese Guangdong people. It is an inherited genetic disease. In Korea, they found limited flow of this gene from southern China:

http://jkms.kams.or.kr/2002/pdf/08475.pdf

It is said that during the Ming Dynasty, there was a war between China and Japan fought in Korea. 2/3 of the infantry came from southern China. Admiral Chen was from Guangdong. After Ming fell the Manchu Qing, his grandson fled to Korea and found refuge. His descendants still live there today.

During the Imjin war, northern Chinese general Li Rusong (of Korean descent) did not like the southern Han troops and often withheld food and payment from them. Thus, they resorted to looting and raping the local Korean population. Of course, not all mixing between Chinese and Koreans were forced. Since the fall of Han Dynasty, there has been commercial activity between southern China and Korea. Many mixed and settled in Korea undoubtedly

Can you please provide evidence of Southern Chinese mixing with Korean population in Korea?

The link you have cited only states that a specific codon is related to Koreans.

A codon is a small part of a gene.

There are 1000 codons in a gene and over 100,000 genes in a human.

The research was done by geneticists, they are scientists not anthropologists.

I did not imply there was massive mixing between southern Han and Koreans. The authors (who are Korean btw) themselves state that there must have been some gene flow from south China to Koreans.

When Ming fell, the grandson of Admiral Chen Lin (who was from Guangdong) fled to Korea and found refuge. The Korean king remembered his grandfather's gratitude and fight against Japan during the Imjin War. The descendants of Chen Gongsu can still be found in Korea today. Maybe they brought this genetic disease to Koreans?

No they only say the codon found was found also in Chinese population.

And if you want to look at it this way, then there are probably people in Europe and Africa who have some codons that are similar to Chinese people.

This study is only trying to prove the codon is similar to both Chinese and Koreans.

It does not prove there was any significant mixing between Koreans and Southern Chinese.

In other words, you made information up yourself about Chinese migrations and settelment in Korea during the Imjin war, which is nowhere to be found in any Korean historical records.

And I bet you arent even Chinese.