Another setback yesterday for free speech, as Colorado car salesman Joe Gordon was sentenced in Bangkok to two-and-a-half years jail for insulting the king of Thailand. Gordon, who was born in Thailand, had posted on his blog extracts from a banned biography of king Bhumibol Adulyadej and was arrested earlier this year while (according to the BBC) visiting Thailand for medical treatment.

US consul-general Elizabeth Pratt expressed concern at the case: “We continue to respect the Thai monarchy but we also support the right of expression which is internationally recognised as a human right.” In practice it is widely recognised that the lèse-majesté laws go far beyond their ostensible purpose of protecting the dignity of the monarchy — the king himself has questioned their usefulness — and are increasingly being used to stifle political dissent.

In many ways, political debate in Thailand is robust and far-reaching.

This year’s election campaign was vigorously conducted, and resulted in victory for the anti-establishment forces of exiled leader Thaksin Shinawatra and his sister Yingluck, who became prime minister. Clearly the censorship, such as it is, is limited in its effectiveness.

But the players in the political game, whatever their real attitudes, all know to maintain a veneer of respect for the monarchy. Other topics can be canvassed freely and even acrimoniously, but talk of the king and the royal family is limited to vague generalities.

Indeed, I’m not going to talk about the king much, since I have no desire to end up in the same place as  Gordon. But as often happens, the effects of censorship are more interesting than what the censorship is actually trying to protect.

Despite high-profile cases such as this one, foreigners are not the main target of the laws. Gordon is most unlikely to serve another two years in prison; most probably he will be quickly pardoned and deported, as other offenders have been in the past — such as Australian Harry Nicolaides in 2009.

There is no way the Thai government can ever hope to control the volume of material on the internet posted from overseas.

The purpose of the law is domestic: to chill debate on certain topics and maintain an aura around key institutions that protects them from criticism and from thoughts of fundamental reform.

This is especially important now because the Thai establishment is facing a more uncertain future than ever. The king has just turned 84 and has been in hospital for more than two years; the prospect of a messy and disputed succession comes ever closer. And although Yingluck has governed cautiously so far, her supporters — and especially her brother, whose return is seen as inevitable — have plenty of scores to settle with the military and the palace circle that have done so much to try to keep them from power.

So Thailand seems to be sort of on hold, waiting for a crisis without knowing when or how it might happen. The truth and reconciliation commission, established by the previous anti-Thaksin government, reflects that, expressing concern about censorship but unwilling to give up a bulwark of the establishment. As a story in this morning’s Nation reports, the best it can do is to recommend that “punishments should not be excessive or without direction or without regard to the sensitivity of the case as this might subsequently affect the monarchy domestically and internationally”.

In this environment, it is only superficially a surprise that Yingluck has turned out to be just as keen as her predecessors on enforcing the lèse-majesté law. In reality that’s just what one would expect: loyalty to the form, while working behind the scenes to manipulate the substance in her own favour.

That’s how censorship works. The real debate is hidden, but it casts a sort of twisted shadow into the public arena. But the secrecy itself is destructive, and eventually the sense that there is something to hide hurts the system more than publicity for the hidden thing ever could.

In one sense at least the respect for the king is certainly real: everyone, including both Yingluck and the generals, dreads what might happen when he dies. But the reckoning can’t be put off forever.