The Persians were held to a 1-1 draw at the Ha Noi Millennium Stadium.
“I am not satisfied with my players. Our team members did not put up a good performance against Singapore. Furthermore, I think the referee favored the other side in this match and wrongly ruled out our two goals as offside,” Iranian coach Gholamhossein Peyrovani said.
Malaysia and Vietnam are taking part in the tournament as well.
The final match will be played on October 2 at the Thong Nhat Stadium.
The first-placed team will receive a cash prize of $20,000, the runner-up will get $10,000, and the third-placed team will earn $5,000.