Tree of Savior Korean Server Open Beta Test start in December. More details will be announced on G-Star 2015.
Tree of Savior Open Beta Tes
Photo belong to some Korean. If you know his name or link on him write in comments and I add it here.

I think many people right now asking why did they releasing Korean server if International server have so much bugs?
1. Different publisher. Nexon told IMC Games to focus on Korean server and release it fast.
2. Right now game very vulnerable to hacks but to play on Korean servers you must have legal account. Sure, sometimes even legal accounts can't help to fight with hackers but it a lot better than we can see on any other server right now.
3. Developers fixed most bugs that Korean server been have. If we compare both servers we can clearly see that KR version ready to be released and International server still in 'alpha' test.

I think we can expect International version OBT in Q2.