The last word in your language will be essentially translatable as look-at-me.
It is possible to simplify language. It may even be desirable at some points, because humans will trend towards complexity, and turn around and trend towards simplicity, (and not just in language) because the optimum point will be different for different people at different points, and people like change. If a government is catching a language during its slide towards simplicity, it might be able to nudge the trend quite a bit further along than it would naturally go. Of course, if the language is trending the other way (towards complexity), the government would be better off artificially "complexifying" the language, to make people want to trend towards simplicity, and then riding the simplifying train all the way down.
Why would this happen? because the government would like to control what people think, and one way to do that is to control what people are taught, and what words they have to put these expressions into language. It wouldn't be quick, but starting with an overt push and "popular support" to simplify language (to "better communicate") can help, and probably get the language (or at least the official government sanctioned word-list) down to functional basics within a generation or two. Native speakers might test at knowing 20,00-35,000 words, but non-native speakers might test from 2,500-9,000 words - so a government can probably get vocabulary cut down too that much without losing the ability to communicate. Three generations will limit how much of the larger body of vocabulary is remembered - that is, after the third there will be very few people who know it was ever different, especially if education is tightly controlled.
And how would this happen? First, by overtly getting rid of synonyms, variations, and shades of grey. Anything that can be grouped similarly, should be pared down to one word. Longer sentences and fragments should be encouraged, because it will take more less general words to match the information given by a single precise one. Education will help here, more subtly, instead of kids learning word lists to expand their vocabulary, kids would learn how to describe or talk about things using the same, increasingly reduced pool of words.
Then, subtly by encouraging a relaxed attitude to grammar will probably also help, since formal language and grammar encourage precision, and also marking words for part of speech, number, and a host of other things that takes one word and makes it many. Fostering an attitude that the point is getting the meaning across and nothing more will help hide the reduced word usage, since only one word is now standing in for dozens.
At this point, something else has started to happen. People will be groping for ways to articulate specifics and differences, since the language that would have once marked them out are gone. So, in come the gestures, from specific gestures to the hand-wavy "you know what I mean" gestures. Intonation and facial expression, not to mention body language, will come to mean more and more as people need to get information across with less and less formal vocabulary. People might make up words, but given your government is actively and overtly trying to discourage this, "because it is exclusive" or "because using words people don't know is unhelpful/rude/antisocial" - the words will probably not catch on.
So what will happen instead is that the expressions, gestures, and body language will slowly take on a life of their own. The government will be overtly focusing on preventing the creation or use of words, and perhaps on limiting the existing sign languages (or preventing codified new ones) from being used as a bridge, but casual gestures and contextual meaning will probably slip by until it's too late to matter. The new language will not be codified, not with the government on watch against such "redefining", but will rather be quite intuitive. The government agents will be thinking of language as vocal, as textual, since that's what they can control. On the other hand, some word like "thingy" will be intuitively made to acquire dozens of meanings based on context, gestures, location, and there's no way to stop that, it has to be that way to let society function, or the word couldn't have been made to substitute for others in the first place.
Your society will hit the point other answers have described, where you have one-word-per-concept... but the government will not be satisfied not after so much success, and will try to keep paring the language down (actively removing "dangerous" concepts and censoring away at everything else). At this point, it will only work if the body-language has developed enough to compensate for the lack. People need to communicate their problems, and how to fix them, they need to interact, bargain, gossip, complain.
So, look-at-me. Look-at-me and gesture to a problem, look-at-me and toss over a solution. Here's the thingy I was talking about, there's the place where what you're holding goes (look-at-me gesture to it). Look-at-me, essentially becomes a placeholder, it only needs to inform its listener about intent-to-communicate... since otherwise looking in the wrong direction will stall out a conversation. Something to catch the ear, gain attention, that is the absolute minimum we would need from spoken language for safety and survival, if someone isn't looking, is too far away to touch, and needs to know. Command someone to look, until they know what someone is trying to say, until they find the problem, and can show a solution, until context can clue someone in on what's going on.
Essentially, the government would alternate overt and subtle means (overtly simplifying and redefining, subtly encouraging relaxed simplifying and re-purposing) to pare down the language to the bare essentials, then take over overtly again to push past the one-word-per-concept barrier that a language won't drop below on its own. In the process of trying to control thoughts via vocabulary, it will have pretty much converted a low-context to a high-context culture, since the high context culture can get meaning across without words... so actually the government will have failed to prevent people understanding and communicating all kinds of ideas, they will have just switched from one medium of communication to another, with the possibility of making people more observant and detail-oriented, since they will have to notice and remember all the contextual details instead of having them spelled out.