This seems like it should print the thread ID of the first thread in the snapshot, but it always prints 0. What is wrong with it?

import ctypes
from ctypes import wintypes

pid = 1234

TH32CS_SNAPTHREAD = 0x00000004

kernel32 = ctypes.windll.kernel32

class THREADENTRY32(ctypes.Structure):
    _fields_ = [
        ('dwSize',             wintypes.DWORD),
        ('cntUsage',           wintypes.DWORD),
        ('th32ThreadID',       wintypes.DWORD),
        ('th32OwnerProcessID', wintypes.DWORD),
        ('tpBasePri',          wintypes.LONG),
        ('tpDeltaPri',         wintypes.LONG),
        ('dwFlags',            wintypes.DWORD)
    ]

CreateToolhelp32Snapshot = kernel32.CreateToolhelp32Snapshot
CreateToolhelp32Snapshot.argtypes = (wintypes.DWORD, wintypes.DWORD, )
CreateToolhelp32Snapshot.restype = wintypes.HANDLE

h_snapshot = kernel32.CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, pid)

LPTHREADENTRY32 = ctypes.POINTER(THREADENTRY32)
Thread32First = kernel32.Thread32First
Thread32First.argtypes = (wintypes.HANDLE, LPTHREADENTRY32, )
Thread32First.restype = wintypes.BOOL
thread_entry = THREADENTRY32()
thread_entry.dwSize = ctypes.sizeof(THREADENTRY32)

if kernel32.Thread32First(h_snapshot, ctypes.byref(thread_entry)):
    print(thread_entry.th32ThreadID)