Wong, who was just 17 years old when he became the face of the 2014 student-led Umbrella Movement democracy protests, faces a maximum three-year jail term. The sentence will be delivered at 2.30 p.m. (0630GMT). Long-time activist Agnes Chow will also be sentenced together with Wong and Lam.
Wong was not a leading figure in last year's pro-democracy and anti-China protests, but his continued activism has drawn the wrath of Beijing, which sees him as a "black hand" of foreign forces.
He disbanded his pro-democracy group Demosisto in June, just hours after China's parliament passed a sweeping national security law for Hong Kong, punishing anything Beijing considers to be subversion, secessionism, terrorism and collusion with foreign forces, with up to life in prison.
Wong also faces charges of participating in an unauthorized assembly in October 2019 and on June 4, 2020 over a vigil commemorating the crackdown on protesters in and around Beijing's Tiananmen Square in 1989.