If you play BDO on steam and your location is in SEA but after you download bdo from steam and the client is TR/Turkey server instead of SEA don't sing up yet, don't patch it yet and don't uninstall yet, Instead of reinstall it from steam you just need to download SEA server client from https://www.sea.playblackdesert.com/Data/Down/  after that, just copy paste all the files from SEA client directory to your "BlackDesert" folder on C:\Program Files (x86)\Steam\steamapps\common . It will change from TR/Turkey language and server into SEA. 

i face this issues twice and manage to change it again from TR/Turkey to SEA. hope it works for you Good Luck..

Thanks you it's work for me

if i used to have an account on bdo sea steam will the account come back? because I can't login to the bdo account from steam until now

Great it worked. You can copy after the official client (Data/Down) patched full. Then paste to steam.
I am not sure whether when you copy, you better exit steam or not
When you start the game, it will have long recheck. (If nothing go wrong it should able to press play) Else it redownload thailand, then you know your screw up. Copy again maybe.

Thank you so much

If bdo has an update, will steam download the data of the turkey server or will it still download the data of the sea server?