Update
I developed the following workflow in an attempt make the process a little more robust.
First, I created a directory and test file with no spaces or special character. Then I opened a command shell to confirm that the command is working as expected with simple characters. Once it is working as expected, I saved the command history as shown in the screen cap below.
Next, I imported the history as a table in Mathematica
SetDirectory[NotebookDirectory[]];
histtable = Import["hist.txt", "Table"]
(* {{"cd", "Dropbox\\WolframCommunity"}, {"dir", "/b",
"e:DocTest\\testdir"}, {"doskey", "/History", ">", "hist.txt"}} *)
I see that the second to the last element of the list contains the DOS command that I want to process. So, I created a function to replace my command list with simple names to arbitrary names.
cmdfunction[dir_] := {"cmd", "/c"}~
Join~(StringReplace["testdir" -> dir] /@ histtable[[-2]])
Now, we can test if RunProcess works on our troublesome folder.
RunProcess@cmdfunction["тест 2"]
(* <|"ExitCode" -> 0, "StandardOutput" -> "test file 2.txt
", "StandardError" -> ""|> *)
It appears to work. Perhaps, this workflow could be adapted to prepare other DOS commands for RunProcess to take out some of the guesswork.
Original
I broke the command up and got it to work on my system (note that I did it in E:\DocTest).
RunProcess[{"cmd", "/c", "dir", "/b",
"E:\\DocTest\\тест 2\\"}]
(* <|"ExitCode" -> 0, "StandardOutput" -> "test file 2.txt
", "StandardError" -> ""|> *)