Singapore's PM testified in court in a lawsuit over the blogger’s alleged role of sharing a Facebook article and spreading false claims linking the leader to Malaysia’s state fund 1MDB money-laundering scandal.
For critics, PM Lee’s defamation suit is the latest example of the tightly-regulated city-state's government being heavy-handed and seeking to silence dissent online.
Singapore's leaders have frequently turned to the courts to take on critics, ranging from political opponents to foreign media outlets, and insist such action is necessary to protect their reputations.
Taking the stand at the start of the trial, Lee accused Leong of making "malicious and baseless" allegations, which had undermined the government's "integrity and honesty".
The article that Leong shared, originally published in a Malaysian news portal, alleged that Singapore's PM was the target of an investigation in Malaysia over the 1MDB state fund.
Billions of dollars were looted from the investment vehicle in a scandal that involved Malaysia's former leader Najib Razak and his inner circle.
Lee, 68, also said he suffered damage to his own reputation.