The result moved Iran to six points at the top of the group where they will be guaranteed a top-two finish. They sit two points above the United Arab Emirates while Palestine are third with one point.
Iran broke the deadlock in the 24th minute when Milad Mohammadi released Ghayedi into the box where the 25-year-old took his shot from a tight angle and beat the keeper as he guided the ball into the far bottom corner.
Iran dominated possession and had several opportunities to extend their lead but failed to convert their chances as Hong Kong frustrated their more illustrious opponents, much to the disappointment of Iranian coach Amir Ghalenoei.
Hong Kong, who made their return to the Asian Cup after 56 years and are 129 spots below Iran in the rankings, remain winless and are bottom with no points after losing to UAE in their group opener.
Iran play UAE on Tuesday in their final group game which will effectively decide who tops the table and gets a more favourable draw in the knockout stage.
