At least four flares were set off by Vietnamese fans during fixtures involving the national team against Indonesia and Thailand.
The AFC fined the VFF US$13,750 for their failure to stop Vietnamese fans from lighting a flare during the tie between Vietnam and Indonesia.
The VFF were fined an additional US$25,750 as three flares were set off during the clash between Vietnam and Thailand.
The AFC also warned that stricter discipline will be enforced in the future if flares continue to be used at international events.
In 2017 and 2018, the AFC fined the VFF US$12,500 and US$15,000 after fans set off flares at the Asian Games in Indonesia and during a 2019 Asian Cup qualifier against Cambodia in the Phnom Penh Olympic Stadium.