DWORD WINAPI mHandler(LPVOID sId) {
...
arr[(int)sId]
...
}

int id=1;
CreateThread(NULL, NULL, mHandler, (LPVOID)id, NULL, NULL);

warning C4311: 'type cast' : pointer truncation from 'LPVOID' to 'int'
warning C4312: 'type cast' : conversion from 'int' to 'LPVOID' of greater size

// parameter on the heap to avoid possible threading bugs
int* id = new int(1);
CreateThread(NULL, NULL, mHandler, id, NULL, NULL);


DWORD WINAPI mHandler(LPVOID sId) {
    // make a copy of the parameter for convenience
    int id = *static_cast<int*>(sId);
    delete sId;

    // now do something with id
}

DWORD WINAPI mHandler(LPVOID p)
{
    INT_PTR id=reinterpret_cast<INT_PTR>(p);
}
...

INT_PTR id = 123;
CreateThread(NULL, NULL, mHandler, reinterpret_cast<LPVOID>(id), NULL, NULL);

static_assert(sizeof(int) <= sizeof(LPVOID),
              "Use new int() - cannot fit int to LPVOID");
int id = 7;
LPVOID idP = 0;
memcpy(&idP, &id, sizeof(id));
CreateThread(NULL, NULL, mHandler, idP, NULL, NULL);

void mHandle(..., LPVOID idP, ...)
{
   static_assert(sizeof(int) <= sizeof(LPVOID),
                 "Use new int() - cannot fit int to LPVOID");
    int id;
    memcpy(&id, &idP, sizeof(id));
}