唔該巴打 不過我已經搵到點解我由90日變到得返30日
If you satisfy any of the following conditions, you can travel to or transit through Korea without a visa. You will be able to stay for up to 30 days in Korea.
1) Frequent Visitors : You have entered Korea at least 4 times within the past 2 years, or 10 times in your total travel history. Also, you have never violated Korean laws or overstayed in Korea before.
Source:
https://www.visa.go.kr