Motahari found the back of the net in the 13th minute after Thailand goalkeeper Lakhonphon Nopphon made a mistake and his shot was deflected by the Iranian forward into the goal, Tehran Times reported.
Salmani also netted the second goal from the penalty spot in the 80th minute at the SC Sports Centre Stadium.
Iran started the campaign with a goalless draw against Saudi Arabia in Group B and defeated Vietnam 4-0 and Mongolia 3-0 in their following matches.
Reza Enayati’s side will play the winners of Palestine and Hong Kong in the quarterfinals.
With more than 12,000 competitors from 45 nations and territories, the 2022 Asian Games has more participants than the Olympics.
Iran has sent 289 male and female athletes to the Games in 34 sports events.
MNA