I guess "chapati" is foreign word and should be italicized in a text. But what about plural? The foreign word is actually chapati, and the plural is made using the English "s" (even if, maybe, chapati is like "bread", singular). What's correct?
Regarding chapatti itself, I recall that the word was not set off either in quotes or italics the first time I read it in a novel several decades ago.
This may be due to the fact that it's a British novel that deals with a former British possession, or that it's a first-person narrative by a character who is no Oxford don, but I incline toward the feeling that certain words, especially those relating to food, are not subject to the usual arm's-length treatment other words might be. We refer to tortillas, empanadas, brioche, linguini, sauerbraten and borscht all without that crutch, and we get along just fine.
Normally we reserve italics for foreign words for which we already have a ready English equivalent (frisson for "thrill"), or for which no comparable word exists in English (gemütlichkeit), or which the writer or editor decides is too recondite (kulturny)—and it is worth noting that the decision really rests on the person or organization who puts the words up for publication.
It is sometimes hard to avoid the suspicion that italicization can be overdone, or used as an affectation. And styles do vary. The New Yorker seems to italicize foreign words within an inch of their lives, while other publications take a much milder stance on the matter.
Full disclosure: I have asked a question similar to this one and came away feeling no real sense of closure on the subject.