Bangkok: An Australian expert on south-east Asia has warned the potential for future turbulence is high in Thailand as the country's military entrenches its rule.

Nicholas Farrelly from the Australian National University (ANU) says a "fluid situation" in Bangkok after a coup in 2014 and the death last year of King Bhumibol Adulyadej is complicated by the potential escalation of separatist violence in southern Thailand, where more than 6500 people have been killed in a little-reported insurgency since 2004.

Firefighters try to extinguish the fire after a bomb hidden in a car exploded in southern Thailand in May. Credit:AP

"The slow-burning character of the three main issues confronting Thailand – a new king, entrenched military dictatorship and a resilient insurgency – ensures that the country's triple threat will not disappear overnight," Dr Farrelly wrote in a paper for the Lowy Institute that was released on Tuesday.

The paper echoes growing concern about a rolling retreat to authoritarianism across the region, including in Cambodia, which has entered a vicious vortex of political violence; Malaysia where a draconian security law is back in force; and the Philippines where a popular strongman is turning a blind eye to thousands of extrajudicial killings under the guise of a drugs crackdown.