Wake Thrasher

• WWizards of the Coast2008-08-01
  Official Ruling
  If permanents you control become untapped during your untap step, Wake Thresher’s ability will trigger that many times. However, since no player gets priority during the untap step, those abilities wait to be put on the stack until your upkeep starts. At that time, all your “beginning of upkeep” triggers will also trigger. You can put them and Wake Thresher’s abilities on the stack in any order.

Rulings via Scryfall