Prime Minister John Key says New Zealand's position on the Commonwealth Heads of Government meeting (CHOGM) is unchanged despite the detention of an MP in Sri Lanka and two leaders deciding not to attend.
The three-day meeting in the capital Colombo starts on Friday.
Sri Lanka is accused of committing war crimes, particularly during the final months of the civil war in 2009. That has prompted calls for leaders to boycott the meeting and oppose Sri Lanka as chair of the Commonwealth.
India's Prime Minister Manmohan Singh and Canada's Prime Minister Stephen Harper say they won't attend over concerns about human rights abuses.
On Sunday, Green Party MP Jan Logie had her passport confiscated and was detained for three hours.
John Key said on Monday that he would still go to Sri Lanka because New Zealand believes it is more constructive to engage. However, he said he would directly raise concerns with Sri Lanka's president about historic allegations and more recent incidents.
Mr Key will also travel to Thailand for a trade related visit. A planned visit to Philippines may not go ahead due to the devastating and fatal Typhoon Haiyan.
Jan Logie says the way she was detained by authorities in Sri Lanka shows the country does not allow free speech and is not a democracy.
Ms Logie was in Sri Lanka to talk to people pushing for an independent investigation into accusations that government forces committed war crimes in 2009.
However, immigration officials shut down a news conference called by her and an Australian Greens senator before taking their passports and holding them in a hotel for three hours.
Just before leaving Sri Lanka, Ms Logie said the incident strengthens the case for New Zealand to boycott the meeting.
Greens co-leader Russel Norman says that if John Key is going to the meeting he should speak out loudly against human-rights abuses in Sri Lanka and also oppose Sri Lanka's bid to chair the Commonwealth for the next two years.