Sukhothai

Thank you Craig! He toured the archaeology site by bike a few weeks ago, and writes that he expected the Historical Park to be selling the below issue along with the postcards, but could not find the set there, nor anywhere in the town. But had luck at the amazing Phra Khanong philatelic counter in Bangkok. The red 'Inlet Gate' impression stamped on tickets purchased to access the very center of the historical park. 

The Sukhothai Historical Park set showcases remains of the 13th-14th century Sukhothai Kingdom capital, which spans over 70sq km. The first archaeological excavation was undertaken in 1907 by the crown prince, Vajiravudh. This set was released for the park's official opening to the public.