Iran got off to a fine start, taking the lead in the first minute off a set-piece situation when Salar Aghapour teed-up Mahdi Karimi, who finished into the bottom corner of the net from the top of the arc.
Saeid Ahmad Abbasi scored his eighth goal of the tournament four minutes later at the Bangkok Arena.
Jirawat Sornwichian pulled a goal back shortly after receiving a good pass from Muhammad Osamanmusa.
A relentless Iran responded two minutes later off a set-piece situation when Mohammad Reza Sangsefidi lofted the perfect cross to an unmarked Ali Asghar Hassanzadeh to volley home to regain its two-goal advantage.
Thailand, desperate to reduce the deficit in the second half, opted for the power play, but the move proved costly in the 34th minute as Mohammadi gained possession in his area before lofting the ball over to score Iran’s fourth to confirm his nation's 13th AFC Futsal Asian Cup title.