She wowed both judges and spectators alike with her confident display in the costume by designer Minh Tu Nguyen.
The other countries to place in the contest were the USA in second position, and Ukraine in third.
Ha Thu had already achieved a third place in the talent competition at Miss Earth 2017.
In addition to these honours, the organizing board chose Ha Thu as one of 6 contestants to feature in a photoshoot advertising a luxury resort in Tarlac province. Thu and contestants from Switzerland, Bolivia, Zambia, Serbia, and Puerto Rico planted trees, gave interviews and explored the resort.
The swimsuit and evening gown competitions will transpire on October 14 and 28. A Q&A session will be held on October 25-29.
The grand finale is scheduled to take place on November 4 in the Mall of Asia Arena, Manila, the Philippines.