This is one of the great curries of northern Thailand. Gaeng means curry in Thai and hang lay in Burmese a kind of pork curry. This gives you an inkling of the cultural fusion that shaped this dish’s introduction into northern Thai cooking, particularly here in Chiang Mai.
A little back story is helpful in grasping the close cultural and geographical links in the north and how this dish evolved. Chiang Mai was founded on the banks of the Mae Ping river by King Mengrai in 1296. The northern regions, including Burma, what is now northern Thailand, and Laos were loosely bound together culturally in various kingdoms that were eventually brought together into the Lanna Kingdom in the 15th century. The alliance was disbanded in in 1775 and the northern provinces bordering Siam were eventually annexed to the Kingdom of Siam in 1892, along with the north’s indelible cultural links to its past in tact.