Thailand's junta won approval from the king Tuesday for an interim constitution mapping out year-long political reforms expected to curb the influence of fugitive ex-premier Thaksin Shinawatra.

It was the first time the revered but ailing King Bhumibol Adulyadej, 86, had granted an audience to coup leader General Prayut Chan-O-Cha since the military seized power two months ago.

The document, published online late Tuesday, offers an amnesty from prosecution to the generals who seized power in the May coup.

It also hands the junta sweeping -- if vaguely-defined -- "national security" powers and allows them to rule in parallel with a national assembly appointed by the king on the advice of the military.

Membership of that assembly will be strictly controlled, with many of the main players in Thailand's turbulent politics seemingly barred by a clause prohibiting anyone who held "a position in any political party in the past three years".

The military will further deepen its grip on power with a 250-strong council which it will hand-pick and charge with recommending sweeping reforms.

Prayut has said the overhaul of the political system will be complete once a new, permanent charter is endorsed, opening the way for fresh elections.

But he has ruled out holding elections until around October 2015, despite appeals from the United States and the European Union for a return to a democratic path.

The May coup was the latest chapter in a long-running political crisis broadly pitting Thaksin's billionaire family and its supporters against a royalist establishment backed by parts of the military and judiciary.

"The goal is to utterly destroy the influence of Thaksin," said Paul Chambers, director of research at the Institute of Southeast Asian Affairs in Chiang Mai.

"But a military government and new reactionary constitution will instead tend to build sympathy and more support for Thaksin from rural and impoverished Thais."

- Appointed MPs? -

Story continues

The army chief seized power after nearly seven months of protests saw 28 people killed and paralysed the government of former prime minister Yingluck Shinawatra, who is Thaksin's sister, and her Puea Thai Party.

The junta has severely curtailed civil liberties by muzzling the media and summoning or detaining hundreds of political activists and anti-coup protesters.

Some observers predict the permanent constitution will enshrine reforms that could see the lower house of parliament becoming partially appointed, like the former upper house.

"The conservatives know that if they let a normal election happen again, the Puea Thai Party and Yingluck maybe can win another landslide," said Kan Yuenyong, executive director of the Siam Intelligence Unit think-tank.

But Kan added that there was also "a lot of political conflict within the conservatives themselves", so it was unclear how radical the reforms would be.

The junta chief received approval from the king -- the world's longest-serving monarch -- to run the country days after the May 22 coup.

On that occasion he did not meet Bhumibol, who has lived at his seaside palace in the resort of Hua Hin south of Bangkok since leaving hospital in August 2013 after almost four years.

Some see the long-running crisis as a struggle over who will hold the reins of power when Bhumibol's more than six decades on the throne eventually end.

The army said the takeover was necessary to restore order.

But critics accuse the junta of using political unrest as an excuse to purge Thai politics of Thaksin's decade-long dominance.

The populist politician, who was seen by his opponents as a threat to the monarchy, was ousted by royalist generals eight years ago and lives in Dubai to avoid a jail term for corruption.

Yingluck was last week given permission by the military to travel overseas for the first time since the coup.

She is expected to attend Thaksin's 65th birthday party on July 26 in France, but has vowed not to flee into self-exile.

Since taking power, the junta has imposed martial law, banned public rallies, censored the media and summoned several hundred people for questioning.