That's wrong. Devanagari script is used only for Hindi, and for the official version of Sanskrit. Perhaps a few other languages like Marathi use a modified Devanagari.
In reality, Sanskrit can be written in any script, and was usually written in the local script before the colonial period.
Thai script looks more like teligu forgot about the language itself.
Well as far as my knowledge Devanagari is the language and Sanskrit is the scripture. Why I said is because in ancient Tibet; before the Tibetan prehistory, an era before(600 ) BCE Tibetan only had their native tribal language but they do not have the scripture nor the mainstream religion. And the tribal language is more then one language. But as the empire Songtsen Gampo started to expend his military from northern Afghanistan to southern Bay of Bengal and some parts of northern Burma. He had send 100 bon buddhist students to study sanskrit from Kashmir, India. At that time both Tibet and India share the open boarder in Kashmir. Therefor, people who lived btw India and Tibet belongs to specific tribal who's mother tongue is Devanagari. Out of those 100 students only couple survived and came back to Tibet. Later one student who's name is Thu-mi-samboda went back to Kashmir again and with the help of Kashmir Brahmin he invent Tibetan script out of sanskrit script and invent 1st mainstream Tibetan alphabet from sanskrit and from then all the religious text of Lord Buddha and all the mythology of tibetan history and literature were all documented in Tibetan script which originated from sanskrit.
About Devanagari suppose to be language of GOD. It is spoken only by people who's mother tongue is Devanagari (more like people who belongs to indus valley) modern day boarder btw southern Tibet and Northern Ancient India. And when they speak they only use the words out of sanskrit scriptures which is different from our mainstream language, be it Tibetan, Punjabi, Urdu, or Teligu and etc... It's like for us we understand devanagari only after studying it but for those people they can be able to speak it before they even have to study their language. Kyirong is the Tibetan region where those Tibetan tribal speaks devanagari, and its the limelight of Silk Route and their roots were known Newari clan from Nepal mixed with Tibetan clan from Tibet. Most of the finest goldsmiths and artist from Tibet were known to be from that region and no offense their caste were consider lower caste in Tibet even though they are one of the most advance, well skilled and talented people from ancient Tibet.
Now in nutshell that's my difference btw scripture and language!