Movement from a democracy to an autocracy seeks legitimacy in legal and democratic terms. Because the transition is from democracy, there is either implicit or explicit democratic action that is taken to limit or essentially destroy democratic power. This is seen throughout history. Why an autocracy needs such legitimation is mostly an issue of propaganda, but it is universally sought.
The Lex Titia was a law granting the Second Triumvirate power over democratic laws and institutions. Typical means were employed to have such a law passed, mainly control over the military, death sentences on the killers of Julius Caesar (which was extended to political enemies), and of course bribery and intimidation, threats, lies, murder and corruption.
In Juntaland, the same thing applies, but of course at a much smaller scale (excepting the the bribery, intimidation, threats, lies, murder and corruption -- which are indeed first rank). The collusion of a few to effectively be permanently placed above the electorate and their political desires, well, that is where we are now with the draft constitution.
Pericles and Direct Democracy
While representative democracy seems obvious, there have been and still are more direct democracies. This indeed is really what is at stake and how a disdainful military conceives of voting.
> Do gardeners working outside of the Parliament’s building or farmers know anything about democracy? Of course not. Don’t talk to me about citizenry. Those people only go to vote because they were paid. -- Prayuth Chan-ocha, 01 January 2016
Indeed, gardeners and farmers do know about democracy, in ways the so-called Prime Minister does not, though that should be obvious since the military is the one who subverts democracy every few years. The military may accuse the electorate of venality (even though demonstrably untrue), yet they are the ones who are disenfranchising the electorate, and at the same time running roughshod over human rights and denying individuals and communities their self-determination.