Vanglemesh is a mysterious country marked on The Discworld Mapp as being in the foothills of the Klatchistan mountains, rimwards of Smale, Ushistan and the Klatchistans. Very little is known about it, except that by proximity it may once have been a conquered satellite of Omnia and it now appears to be a loosely-controlled province of Muntab. As the Atlas says:
Our information about this area is incomplete and its remoteness and the unfriendly nature of the terrain make surveying difficult; details of the hinterland and borders are still uncertain. A footnote adds: (the Muntab Provinces) are an elusive country and subject to sudden changes. Our last survey placed it in its current position.
Presumably Vanglemesht is spoken here. This is one of several blind spots lightly covered in The Compleat Discworld Atlas. All that can be inferred about the country is that it is Rimwards of Smale, Ushistan and the Klatchistan states, and hubwards of the Great Nef and possibly the Tezuman Empire. It is briefly mentioned (as an afternote to the general Muntab region) in The Compleat Discworld Atlas as a nation rich in spices, the most important of which is the Vanglemesht Red Python Chili.
One named visitor is the Lancre witch and fairy godmother Miss Desiderata Hollow, who is known to have brought selected herbs and spices of interest back with her, some of which may well have ended up in the noted herb garden of Mistress Esmerelda Weatherwax.
Given the sound of the name, there might be a link to the Roundworld Bangladesh. Good old Wikipedia describes it as being being bordered by India to it's west, north and east - which given the proximity and relative location of Ghat seems somewhat similar when looking at the The Discworld Mapp - and while mostly low lying, it does feature a hilly region and rivers - on the Discworld Map a river is visible coming out of this Vanglemesh. Bangladesh also has several more mountainous neighbors, such as Nepal, which seems reminiscent of Vangelmesh's location in the foothills of the Klatchistan Mountains as mentioned above.
And if that wasn't enough support for the link it seems that once again, Pratchett has looked to historic place names and etymologies to name places on the Disc: The name Bangladesh may derive from the ancient Kingdom of Vanga (which in turn, interestingly enough, is thought to link to the Austric word "Bonga" meaning Sun God - perhaps a link to the Mountains of the Sun?). "-desh" is linked to the Sanskrit word simply meaning "land" or "country". The area has also been known as "Vangla" (back in 805 AD) and "Vangaladesa" (in the 11th century).
The existence of a Central Howondalandian Veldt, or possibly a prairie, has been inferred from the existence of One-Man-Bucket and a possibly Red-Indian like people on the Disc. This makes Vanglemesh, a place where arid desert may begin to gradate into lusher plains on the way to becoming a thick (Tezuman) jungle, a possibility for an Indian nation, in the North American sense. The Tezuman are a related people, after all, just as Aztecs and Maya were part of the North American Amerind continuum.