Leong's lawyer Lim Tean argued the libel suit was unnecessary as authorities had denied the allegations, adding the Singaporean Prime Minister had "picked on the defendant when there are many others who shared the (defamatory) article".
The defamation suit will run until the end of the week.
On Friday, Lim, who is also an opposition politician, was arrested on suspicion of harassment and misappropriating money and claimed the move was politically motivated. Police denied his claim.
Singapore's leaders are sensitive to allegations of graft, but rights groups frequently accuse them of resorting to tough laws to silence criticism.
Last year authorities introduced a law against online misinformation, which empowers ministers to order the blocking of social media posts they deem false, sparking criticism that it would chill free speech. (Writer & Editor: MBA-SR/RBU, © Agence France-Presse)
Dapatkan update berita pilihan dan breaking news setiap hari dari Kompas.com. Mari bergabung di Grup Telegram "Kompas.com News Update", caranya klik link https://t.me/kompascomupdate, kemudian join. Anda harus install aplikasi Telegram terlebih dulu di ponsel.