BANGKOK — Thailand's main professional association of journalists has protested the arrest on trespassing charges of a reporter who was looking into the assets of a brother of one of the top members of the country's military government.

Nattaporn Weeranont of the Isra News Agency was arrested Wednesday night after going to a Bangkok apartment building believed to be owned by the wife of former Police Chief Patcharawat Wongsuwan, who is also the deputy prime minister's brother.

Nattaporn sought to speak with the building caretaker, who instead called police and filed a trespassing charge.

The National Anti-Corruption Commission, an independent state agency, acknowledged that it is investigating Patcharawat.

The Thai Journalists Association issued a statement Friday saying police were obstructing news and demanding that the charge be dropped.