you can take KMB bus No.23M
Here is the information:
Get On Point:牛頭角總站,牛頭角上 or 喜鵲樓
Get Off Point:順天總站
Fee:$4.2
Times:25 mins(not included the waiting tines and walking times)
KMB bus No.23M information:
http://www.kmb.hk/chinese.php?page=search&prog=route_no.php&route_no=23m
Hope above information can help you!