After a goalless first-half, Iran scored three quick goals at the start of the second period to take the game away from Japan at the Indoor Stadium Huamark and retain the crown they clinched in 2015.
Sara Shirbeigi was the star of the show for Iran as she netted a hat-trick, while Fereshteh Karimi and Fahimeh Zarei also got on the scoresheet.
The result ensures Iran remain the only team to win the event as this year's tournament in Thailand was the second edition of the competition.
Thailand earned their second consecutive bronze medal as they beat Vietnam on penalties after the match had ended 0-0.
