The 25-year-old design student beat 24 other contestants for the crown. Nathalie Oliveira of Brazil was first runner-up and Andrea Collazo of Venezuela was second runner-up.
Jiratchaya added the crown to the Miss Tiffany's Universe title she won last May.
The 2016 pageant, scheduled for November last year, was postponed as Thailand was in mourning following the passing of King Bhumibol Adulyadej.
In its 12th year, the contest was held at the Tiffany's nightclub, famous for its transvestite cabaret, in the Thai seaside town of Pattaya.