Need Advice & Help - Thai Fan lost contact In Ulsan, Korea

The Embassy would be the best place to go to in this instance. It may take them time to get back to you as they would need to verify details.
Do you have any details of your friend, like passport number, employer name etc to assist the Embassy.

Thank you for sharing & totally agreed. Already provided those relevant informations (National ID, passport, flight details, etc) to Embassy via email but as you mentioned worry it may take some time.

But the employee business card contain very limited info without complete detail, won't be able to trace. Afraid it may be human trafficking.

In Korea, Is that any social media address / keyword where allow to higlight on missing people issue for public awareness or help?

There are websites online that you can use to check if the business name is a scam.

I am sure there may be a Korean site that gives details regarding the registration of the business name.

I agree that this may well a case human trafficking. Perhaps contact the Korean Embassy with your concerns, give them all the details including the business card and copy the email to the Thai Embassy in Korea as well.

The Korean Embassy may be able to find out if the business is legitimate. I am sure that, as South Korea is a member of the UN, it would have signed  the UN law on human trafficking.