The Ban Singha Tha district, often called the Old Town of Yasothon, is home to several ancient Indochinese painted wooden houses. Well restored, they make this area a pleasant place to wander around to discover the Yasothon of a century ago. It is the most friendly place of Yasothon with the Giant Toad of course;)
You can also visit the Wat Mahathat temple, which is not far away.