If you are asked for more documents, you can supply them and there is no costs. If they reject or cancel your application, and you decide to re-apply, then you would need to pay the 10k again.
Alien registration card is the documentation that allows you to live in Korea. I believe if you look at the Thai embassy website for Korea only Koreans and those with legal residency can apply there.
Anonymous participant - so that doesn’t count as one of the submission days. The embassy in Phnom Penh states it takes 11 business days and they almost always stick to that. Today would be the 11th day (submission on 29th) (usually updates come in evening), but I believe today is a holiday, so might be tomorrow.