Is bak kut teh a dish that began in Hat Yai?
It is not presented as a dish that originated in Hat Yai. It is a Chinese-style dish you find in the Songkhla area, and a menu item that lets you see the varied food culture of the area.
Bak Kut Teh · บักกุ๊ดเต๋
If you want a meal with warm broth on a trip to Hat Yai, pick bak kut teh. Pork ribs are simmered with herbs and aromatic spices. In the Songkhla area it is introduced as a broth dish with the aroma of Chinese herbs. If you eat pork, enjoy it slowly with rice.

The aroma of herbs and spices joins the broth of simmered pork ribs. The color and richness of the broth differ with the recipe. Alternate between the ribs and the broth and enjoy the fragrance.
The broth uses pork too. If you avoid pork, choose another dish.
Bak kut teh is one of the Chinese-style dishes you find in the Songkhla area. It does not mean it was first made in Hat Yai. On a day when you want a different meal from crispy fried chicken, have a meal of pork rib broth and rice.
It is not presented as a dish that originated in Hat Yai. It is a Chinese-style dish you find in the Songkhla area, and a menu item that lets you see the varied food culture of the area.
The typical bak kut teh contains pork ribs. If you avoid pork, it is better to choose another dish. Keep in mind that even eating only the broth means eating a dish made with pork.
If you want to read more about the food and the regions behind it, these sources are a good place to start. Ingredients and recipes can vary from one restaurant to the next.
Sharing image credit: Indradi Soemardjan http://www.indrani.net · CC BY 2.5