"(Our) agencies negotiated an arrangement with her to come to Singapore and perform and to make Singapore her only stop in Southeast Asia," Lee told a press conference in Melbourne, where he is attending a regional summit.
"It has turned out to be a very successful arrangement. I don't see that as being unfriendly."
Swift is currently part way though six sold-out shows in Singapore, her only stop in Southeast Asia.
Singapore's government previously said it had given Swift a grant to play in the city-state, without mentioning the terms of the deal.
The announcement annoyed other countries in the region, with the Thai prime minister saying the grant was made on condition that it would be Swift's only show in Southeast Asia, while a Filipino lawmaker said it "isn't what good neighbours do".
Last month, Singapore's tourism board and culture ministry referred to the economic benefits brought by Swift's concerts around the world due to her popularity, and said the ministry had worked with concert promoter AEG Presents to get Swift to perform in Singapore.
