Thai Prime Minister Prayuth Chan-ocha on Thursday defended his country's rights record since he seized power in a 2014 coup, saying he acted to end months of political instability.

Thailand has faced a deepening rights crisis since the coup with political activity and peaceful gatherings banned, say activists. Military courts have been used to try national security cases, including cases involving civilians, and relations with some western countries, including the United States, have frayed.

"Those who evoke human rights and democracy, look at what happened in the past," Prayuth said in a speech at Bangkok's Government House, days before he travels to New York to attend a session of the UN General Assembly.

"Foreigners have to understand what we're going through... Every country has gone through rough times. We're just a little late. Don't tell us that we abuse rights, you also abuse the rights of others. You create problems too."

Southeast Asia's second-biggest economy is slowly recovering from the events of 2014, when months of street protests and the coup almost brought economic activity to a standstill.

Since then, dozens of junta critics have been held incommunicado in military detention, although the exact number of people detained remains unknown.

During a UN Human Rights Council review of Thailand in May, foreign governments expressed concern over the deteriorating rights situation in Thailand.

Prayuth, a former army chief, said he took control of the country in an attempt to calm months of political crisis. He has repeatedly said he does not want to hold on to power longer than 2017 when a general election is expected to take place.

The military government on Monday said it will prosecute cases concerning national security and royal insult in civilian courts instead of military courts, a change a rights group said was "window dressing" before a UN review.

Thailand's defence minister also spoke at Government House on Thursday and said bombings in Thai tourist towns last month were not linked to Muslim separatists, contradicting an earlier police statement.