One of the men in the video - the younger one - said that he doesn't want the language to die out. It's a common enough problem in many other parts of the world too. My own first language, Welsh, is thought by many to be dying out (though it is easy to disprove that claim.) Several factors in common with Suay have been involved. Firstly, neither language has a vast resource of written text. Welsh was effectively banned by English law some centuries ago, and the books of the time were burnt, though some survived. Children were punished at their schools if heard to speak anything but English - a subject that few of them understood well enough to communicate with. Another video states that the Khmer Rouge forbade the use of Kui/Suay in Cambodia, and it was inevitable that, under duress, habits would change.
As both languages belonged to relatively poor groups, the advent of easier travel made access easier to more plentiful and better paid work elsewhere. As it has always been the younger generations that move away, when they return home, many have lost their mother tongue or become so unfamiliar with it that they use Thai instead (and English in Wales). Entertainment is a driving force too, with most media being in Thai here, and virtually none in Suay. In Wales, the language has survived in greater numbers partly because of the strong cultural traditions there, with two major festivals, both of which draw audiences from far afield, and in one case from all around the world where competitors wear their national costumes, which serves to preserve national identities and greater feelings of "belonging." Without such events, and as the older generation using the language fades away, the language itself becomes redundant. Why learn two or more languages when time and energy can be saved by learning just one? I don't wish to seem prejudiced, but as English is the "preferred" language in so many countries now, is it any wonder that most British people are monolingual now, as is the case, increasingly in Isaan, where dialects and so-called tribal languages (Suay etc) are being lost in favour of "Central" Thai?