How to call a function on a thread?

Question

Programming

There is a DLL that is attacked to the process and it has a function.

BOOL WINAPI DllMain(HINSTANCE dllHistance, DWORD callReason, void* reserved)
{
  switch (callReason)
  {
    case DLL_PROCESS_ATTACH:
    {
      _beginthread(MainCM, 0, NULL);
      break;
    }
  }
  return 1;
}

How can a function be called from WindowProc (main thread) in MainCM thread?
That is, a function call in WindowProc (key interception and, in fact, the main thread.)
And so that it is processed in the MainCM thread?
It's just that if directly, then the crash is due to a call in the wrong thread.

Answer 1

1. Microsoft highly DOES NOT recommend creating threads from DllMain.
2. Where does WindowProc come from?