As a result of the verification, I confirmed that South Korea is definitely exempt from DTV in this part. It is on the online DTV application site (E-VISA). There are many success stories of DTV in the Korean community and they confirm that it is 0 won. This is certain, but I think the problem is that you have to pay in person in Vientiane. Thank you, friend.
according to seoul.thaiembassy, there are 5 countries that are fully exempt from all of the visa fee(korea, malaysia, singapore, tunisia, philiphine(only tourist visa)
For Korean people, DTV is free to apply, and online it's automatically waived — 0 baht. But I heard in Laos people pay in person, so I was just wondering if I need to pay too.