implementation
{$R *.DFM}
Type TBeepProc = Function(dwFreq, dwDuration: DWORD): BOOL; StdCall;

  Function rThread(aValue: Pointer): DWORD; StdCall;
  Begin
    TBeepProc(aValue)(5000, 10);
    Result := 777;

    ASM // Correct return throm tread
      POP EBP
      RET
    END;
  End;

procedure TForm1.Button1Click(Sender: TObject);

  Function GetProcessIDByTopmostWindowClass(aClass: String): DWORD;
  Var wHndl: THandle;
  begin
    wHndl := FindWindow(PChar(aClass), Nil);
    Win32Check(wHndl <> 0);
    GetWindowThreadProcessID(wHndl, @Result);
  End;

  Function GetProcAddrFromKernel(aProcName: String): Pointer;
  Var hMod: THandle;
  Begin
    hMod := GetModuleHandle(Kernel32);
    Win32Check(hMod <> 0);
    Result := GetProcAddress(hMod, PChar(aProcName));
    Win32Check(Result <> Nil);
  End;

Const pMemSize = 32;
Var
  pID, pHndl, tHndl, tID: THandle;
  rMem: Pointer;
  S: DWORD;
begin
  pID := GetProcessIDByTopmostWindowClass('RegEdit_RegEdit');
  Win32Check(pID <> 0);
  pHndl := OpenProcess(PROCESS_ALL_ACCESS, False, pID);
  Win32Check(pHndl <> 0);
  Try
    rMem := VirtualAllocEx(pHndl, Nil, 1024, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
    Win32Check(rMem <> Nil);
    Try
      Win32Check(WriteProcessMemory(pHndl, rMem, @rThread, pMemSize, S));
      Win32Check(S = pMemSize);
      Win32Check(VirtualProtectEx(pHndl, rMem, pMemSize, PAGE_EXECUTE_READ, S));
      tHndl := CreateRemoteThread(pHndl, Nil, 0, rMem, GetProcAddrFromKernel('Beep'), CREATE_SUSPENDED, tID);
      Win32Check(tHndl <> 0);
      Try
        ResumeThread(tHndl);
        WaitForSingleObject(tHndl, INFINITE);
        Win32Check(GetExitCodeThread(tHndl, S));
        Caption := IntToStr(S);
      Finally
        CloseHandle(tHndl);
      End;
    Finally
      Win32Check(VirtualFreeEx(pHndl, rMem, 0, MEM_RELEASE) <> Nil);
    End;
  Finally
    CloseHandle(pHndl);
  End
end;