Thailand has moved one step closer towards entrenched military rule in recent days, after the governing junta granted sweeping powers of arrest and detention to military personnel, drawing harsh criticism from civil society groups and the US government in the process.

Under the terms of the new order, soldiers from the rank of sub-lieutenant and above have the authority to arrest and detain anyone suspected of one of 27 crimes, including extortion, human trafficking, and labor abuse. They are also permitted to search properties without a warrant.

The powers were granted on March 29 by Prime Minister Prayut Chan-o-cha, a retired army general who as the head of the junta — known as the National Council for Peace and Order (NCPO) — has overseen feverish persecution of political dissent.

NCPO spokesman Col. Piyapong Klinphan last week told the Bangkok Post the order was aimed at preventing and suppressing crimes that imperil peace and public order, or that could sabotage the economy.

The move drew rebuke form six prominent civil society groups, including Human Rights Watch (HRW), Amnesty International, and the International Federation for Human Rights (FIDH), who released a joint statement on Tuesday branding the new powers "in contravention of human rights and the rule of law. The new order will "almost certainly lead to violations of Thailand's international human rights obligations," they said.

According to Brad Adams, Asia Director at HRW, the order leaves Thailand at a "pivotal point" that demands urgent intervention from the international community to prevent the rights situation in the country deteriorating further. Adams called for strong public statements from foreign governments and the United Nations to condemn the ongoing excesses of the Thai military.

"General Prayut and his colleagues should be made to understand that if they continue down this course of increasing rights abuses, the Thai government's relations with allies around the world will suffer," he told VICE News.

One government agency to speak out was the US State Department, whose East Asia spokeswoman Katina Adams this week called on the Thai government to limit the role of the military in internal policing and to allow civilian authorities to carry out their duties.

"This includes returning the prosecutions of civilians to civilian courts and providing adequate due process and fair trial protections," she said.

Since coming to power almost two years ago, the NCPO has taken an increasingly repressive approach to government critics, with re-education camps established, civilians tried in military courts, and restrictions on foreign journalists tightened.

"Those who peacefully challenge military rule, including journalists and human rights defenders, face harassment, intimidation, threats, and arbitrary detention," said Andrea Giorgetta, Director of Asia Desk, Southeast Asia at FIDH.

That repression has reached extreme levels, with a political activist facing up to seven years in prison on sedition charges over a Facebook post in which she appeared holding a red bowl with a message from ex-Prime Minister Thaksin Shinawatra written on the side. The military subsequently confiscated almost 10,000 more of the bowls from the offices of three former MPs affiliated with Shinawatra.

Shinawatra, whose political movement is associated with the color red, was deposed in an earlier coup in 2006 and is avoiding corruption charges in exile, while his sister Yinluck was removed from power by the current junta, having swept to election victory in 2011.

Thailand's jolts between civilian and military rule in recent years have been attributed by analysts to a battle between the entrenched Bangkok-based elite and the popular rural-based political movement of Shinawatra, whose social programs directed at countryside communities have provided him with unwavering support among impoverished farmers, even in the face of compelling evidence of his involvement in graft.

The elite have long established ties to both the monarchy and the military, and are the major pillar of support for the current regime. Notably, the NCPO has come down hard on acts seen to offend the dignity of the monarchy — a "crime" known as lèse majesté — with one man threatened with decades in prison for insulting the king's dog on Facebook.

The May 2014 coup was the 19th the country has seen since Thailand formally established democracy in 1932, and the NCPO has said elections slated for 2017 cannot go ahead until a new constitution is established. In late March, the NCPO unveiled a final draft constitution that would allow the military to hand pick the country's senate and potentially select a prime minister.

On Thursday, the US Embassy in Bangkok's spokesperson Melissa Sweeney urged the Thai government to lift restrictions on civil liberties "to allow for an open and robust debate on the draft constitution" ahead of a referendum on its acceptance in August.

"As a longtime friend of the Kingdom, we want Thailand to emerge from this transition period as a strengthened, sustainable democracy that reflects the views of all Thais and protects fundamental freedoms," Sweeney told VICE News.

Thailand's move towards increasing authoritarianism and the possible rooting of the military in the legislature has come at a time when neighboring Myanmar is being lauded for emerging from the political wilderness of almost half a century of military rule.

In December, Myanmar's National League for Democracy (NLD) won a historic election, having battled years of marginalization and repression from the ruling junta. While the constitution adopted by the junta in 2008 guaranteed the military 25 percent of the seats in both the upper and lower houses of the country's Assembly of the Union, it could not prevent the NLD winning control of both houses.

Responding to an earlier version of Thailand's draft constitution — which only included a partially appointed senate — Thaksin Shinawatra drew a stark comparison between the country he once led and its neighbor.

"In reality, it would be like Myanmar before its political reforms. There would be a prime minister, but the real power would be in some politburo above him and the economy would suffer. No other government would want to touch Thailand," he told the Guardian in February.

The powers recently conferred on the military offer little to suggest he is wrong.