SATTAHIP, Thailand • The largest multilateral military exercise in the Asia-Pacific has started in Thailand, with the United States maintaining a scaled-down presence due to the 2014 coup in Bangkok and its calls for a swift return to democracy.

The Cobra Gold military exercise, which was kicked off yesterday by 27 participating countries, has been held annually in Thailand for more than three decades.

This year, the US kept a scaled-down presence. "As in 2015 when the exercise was significantly refocused and scaled down in the light of the military coup, in 2016 it will remain somewhat reduced in size... to reflect US concerns about Thailand's political developments," US Ambassador to Thailand Glyn Davies told reporters. "Diplomatic ties are not on hold with Thailand. Certainly, the military ties are not on hold with Thailand."

Washington has sent 3,600 troops to this year's exercise, the same as last year, said US military spokesman Dave Eastburn.

Thailand's junta has faced repeated criticism for what rights groups say is a deepening slide into authoritarianism since the army took power. Following the coup, the US responded by freezing US$4.7 million (S$6.6 million) of security-related aid and cancelling some security cooperation.

The US and others have called for a swift return to democracy for South-east Asia's second-largest economy, but with the election timeline ever sliding, how soon polls will take place remains unclear. The generals running Thailand had previously made a new Constitution a prerequisite for a general election, but last month Prime Minister Prayut Chan-o-cha said the vote would go ahead in mid-2017, even if it had to be held under an old Constitution.

Since the coup, Thailand, a long-time Washington ally, has cosied up to regional superpower China, which says it supports the Thai military government.

The exercise comes amid rising tension in the region following North Korea's latest rocket launch.

REUTERS