What should I say to customs about my empty Rolex watch boxes sent from the UK?

An expat who has moved to Thailand is seeking advice on how to retrieve empty Rolex watch boxes that were shipped from the UK by their father, with customs inquiring about their contents. There are concerns about how to declare the boxes without raising suspicion of import tax or trade issues, especially since the expat already owns the watches. Commenters suggest various strategies, including being transparent about the boxes' lack of value, stating they are for storage of personal belongings, and asserting they are collectibles with no commercial value.