You don’t need to spend much time in Southeast Asia before you notice how many English-speakers pronounce Thailand’s northeastern neighbor as “Lao” without an s sound. The s is silent, they say. But as every English dictionary (click to listen: American and British) will tell you, Laos does indeed rhyme with “house.” (In IPA it’s /ˈlaʊs/.) Usually two reasons are given by those using the no-s Lao: the locals say it that way, and the French say it that way. The first reason is illogical and the second is incorrect.
Of course Lao is correct as an adjective. Lao food, Lao visa, Lao kip, Lao People’s Democratic Republic (Lao PDR), etc. English uses different words for national names and adjectives for literally every country, but that’s not the issue here.
Because Lao people pronounce it this way.
It’s true that in the Lao language, the country is called Pa- tayht Lao and Muang Lao with no s. The Lao language doesn’t have a final s sound, so grammatically it’s not even possible to say Laos. But the same people who insist on following the s-less Lao pronunciation in English because that’s what locals do still say Thailand, Ireland, Mexico, and Japan instead of Bpra-tayht-tai, Ay-ra, Me-hi-co, and Nip-pon. And in the reverse, this twisted logic dictates that Lao people should say England and España instead of Ang-git and Sa-bain when they speak Lao.
While Lao people will also often use the no-s Lao when they speak English, you should trust Merriam-Webster over a non-native speaker. If someone tells you she has a cousin living in Illi-noise you wouldn’t follow her example.
Because this is how it’s pronounced in French.
No, it’s not. While final s‘s are usually silent in French, sometimes they are not. Autobus, tennis, and lis all have a voiced s, and so does Laos, which you can hear here and here. But even if the French didn’t pronounce the s, we don’t follow them for pronouncing other places: It’s Cambodia not Cahm-bodge, and Paris not Pah-ree.
And it’s not just French and English, most (probably all) European languages, from Icelandic to Portuguese to Greek to Russian, also use a voiced final s sound. Click the grey “In other languages” tab at Collins Dictionary to hear it in over a dozen others.
Where did the s come from?
It’s unknown why the French chose to use an s in Laos. According to Wikipedia (and apparently lots of people who’ve read Wikipedia before writing articles about the country) the French put the s at the end because there were three Lao kingdoms: Luang Prabang, Vientiane, and Champasak. Not only is this unlikely on the face of it, Portuguese missionaries in Macau used Laos with an s (also for reasons unknown) before the French arrived, so perhaps the French, and everyone else, copied them. Additionally, renowned Lao historian Grant Evans makes no mention of this dubious legend in his classic book “A Short History of Laos: The Land in Between” which has a small section (p. xiii-xiv) about the s issue.
Of course this would all be moot if Laos has followed Siam’s lead in 1939 and rebranded itself as Laoland.