Former army commander Prayuth Chan-ocha, who seized power in a coup on May 22, told Thai journalists there were still "unusual movements" like anti-coup protests and martial law was necessary to maintain law and order.

The law, which gives the military almost absolute powers, including the banning of gatherings of more than five people, makes it difficult for tourists to obtain travel insurance; one of main reasons for a collapse in the number of arrivals in a country popular with Australians.

Thailand's King Bhumibol Adulyadej, who underwent surgery to have his gall bladder removed on Sunday, has formally endorsed a new National Reform Council that will draft a constitution to take effect by next July, the Royal Gazette reports.

While the council is supposed to represent a cross-section of Thai society, the military regime has appointed few supporters of former prime minister Thaksin Shinawatra.

Mr Thaksin dominated Thai politics for much of the past decade.

Many of those appointed are critics of Mr Thaksin, who was deposed in a 2006 coup, and his Red Shirt supporters, some of whom have been purged from the ranks of the security services and bureaucracy.

Red Shirt leader Jatuporn Promphan said he was not surprised that Red Shirt supporters or members of the former ruling Pheu Thai Party were not appointed because his group refused to join the council.

"We won't stand in the way of the reform process," he said.

Weng Tojirakarn, another Red Shirt leader, said there was no point in the group participating because the military junta would make the final decisions.

Meanwhile, military, political and religious leaders have led entourages to Bangkok's Siriraj Hospital to sign a book of get well messages for 86-year-old King Bhumibol, the world's longest-reigning monarch.

Doctors said the king's overall condition had improved after Sunday's surgery.

King Bhumibol is seen as a unifying force in the country and his health is a subject of great public concern.