Many rural Thais either cook on a charcoal bbq (see below) or a single gas ring (both outside). Before rice cookers became widely available (and cheap) I understand that the rice was cooked first and then left to cool whilst the other dish(es) were cooked. With a rice cooker it not only frees the bbq/gas ring, it also has the facility to keep the rice warm.
View attachment 14815
Makes even more sense now you explained that.