Earlier this month, contrary to normal practice, Trong, 79, had not been included in official schedules of meetings held with Vietnam's leaders by visiting Indonesian President Joko Widodo and Laos' Prime Minister Sonexay Siphandone.
That led to widespread speculation about his health conditions. State media in their websites on Monday gave prominence to Trong's presence at the assembly's session, which usually is not highlighted, and showed pictures of him smiling with other leaders and standing in the parliament.
Shortly after the chair's opening speech, Trong was seen walking out of the session with the help of aides, according to a Reuters witness.
Trong has been at the helm of the ruling Communist Party since 2011 and holds the top job in Vietnam's one-party political system.
The National Assembly is convening in an extraordinary session to discuss banking and land reforms.
(Reporting by Khanh Vu; Writing by Kanupriya Kapoor, Francesco Guarascio; Editing by Michael Perry)
