The military abolished an earlier constitution after seizing power in a May 22 coup, and the government is currently operating under a temporary charter.
The new National Reform Council was officially endorsed by King Bhumibol Adulyadej. It will advise a drafting committee which will write a constitution that is supposed to take effect next July.
The country's military rulers say the process will lead to elections next year.
The new council is dominated by people close to the country's traditional ruling elite. It shuns supporters of former Prime Minister Thaksin Shinawatra, who challenged the elite and dominated Thai politics for much of the past 13 years.