BANGKOK (AP) — The U.N.'s top human rights official urged Thailand's military government on Friday to ease limits on free speech, especially those restricting debate over a proposed constitution that faces a referendum in August.

U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein also expressed concern about the military's expanding role in policy-making and law enforcement. He repeated a call for all cases involving civilians to be transferred from military to civilian courts.

Thailand has been ruled by a military junta since a May 2014 coup ousted an elected government. The junta uses arbitrary detention to punish critics, and recently announced strict limits on public expressions of criticism or support of the draft constitution, a move directed chiefly against the charter's opponents. Several opponents of the draft charter have already been temporarily detained.

"An open and dynamic public debate on the draft constitution would foster national unity, strengthen the legitimacy and acceptance of the constitution and provide a sense of collective ownership," Zeid said in a statement. "I urge the government to actively encourage, rather than discourage, dialogue and engagement on the draft constitution. This would be an important step in establishing a solid foundation for a sustainable democracy in Thailand."

The statement also noted recent measures broadening the military's role in areas normally under civilian stewardship.

These include an order empowering military officers and paramilitary forces to conduct law enforcement functions such as searching property, seizing assets, suspending financial transactions, banning suspects from traveling and detaining individuals for up to seven days, without any warrant, judicial oversight or administrative accountability.

Zeid said the draft constitution promoted by the military would institutionalize the role of the military in policy-making and law enforcement and permanently legalize all orders issued by the junta chief under Article 44 of the temporary charter put in place after the coup. Under the article, the junta chief is effectively allowed to issue any executive, judicial or legislative order, and he has done so 61 times, the statement said.

"As a matter of priority, I call on the government to suspend the application of these dangerously sweeping laws and orders that have bestowed more power upon the military," Zeid said.