By Larry Jagan BBC Burma analyst in Bangkok

This is a follow-up to his interrupted visit earlier this year when the UN envoy left Burma after discovering a listening device in the room in which he was interviewing political prisoners.

It is unclear whether Mr Pinheiro will be allowed to meet the detained pro-democracy leader, Aung San Suu Kyi.

She has been confined to her home by the Burmese military government since September, after being detained for four months following a clash between her followers and pro-government supporters.

Unfinished business

During his visit to Rangoon, Mr Pinheiro hopes to meet key government ministers, including the Prime Minister, General Khin Nyunt, representatives of the opposition political parties and the ethnic groups.

Paulo Pinheiro wants an end to restrictions on the opposition

His highest priority will be to see Aung San Suu Kyi, but Mr Pinheiro will also be seeking access to other detained opposition leaders.

There is already a lot of unfinished business for the envoy to resume.

One key issue is his planned intensive investigation into allegations that the Burmese army systematically rapes and executes women from ethnic minorities living in conflict areas near the border with Thailand.

He will want to know why the investigation has not been given the final go-ahead even though General Khin Nyunt approved it in principle on his last visit.

But more than anything else he will be trying to impress upon the regime the need for an independent and credible investigation into the events in May, when Aung San Suu Kyi and her supporters were violently attacked while touring in the north of the country.

Mr Pinheiro will be reporting his findings to the UN in a little over a fortnight's time.