>>212605269Khmer and Thai are unrelated and sound almost nothing alike, although they have a lot of shared loanwords from Pāli and Sanskrit. Khmer isn’t tonal, among other things. It’s actually a distant cousin of Vietnamese, although it sounds even less like Viet.
Thai and Lao are practically the same language, though—at least as close as Spanish and Portuguese, and a lot of dialects inside Thailand are more like Champasak than Bangkok. I like Lao a lot; it’s softer than Thai.
I don’t dislike any language, but Dutch vowels are ugly. And some dialects of Swiss German are never going to win any beauty contests. A former colleague of mine, a Frenchwoman who grew up in Basel and speaks Baseldeutsch like a native, learned Dutch, and her daughter declared that thanks to Dutch and Swiss German she officially spoke “the two worst languages.” I actually think the Basel dialect is one of the nicest Swiss dialects, but most people who aren’t from here hate it.