HDY meaning in Regional ?

Hat Yai (Thai: หาดใหญ่, pronounced [hàːt jàj], also Haad Yai or Had Yai) is a city in southern Thailand near the Malaysian border. Located at 7°1′N 100°28′E, it is 946 km (588 mi) south of Bangkok, and has a population of 156,802 (2019) in the city itself and about 800,000 in the greater Hat Yai area. Hat Yai is the largest city of Songkhla Province, the largest metropolitan area in the south, and the third largest metropolitan area of the country. It is often mistaken for being the provincial capital. In fact, Songkhla is the capital and the center of administration and culture while Hat Yai is the business center.