The May index was 56.8, almost identical to the April result (56.7) and the highest result for any month since November 2011.
Describing the result as "absolutely solid", BNZ economist Craig Ebert said it was now very strong on global comparisons.
It suggested business activity and expectations were holding up far better than general economic confidence.
The survey delivered Otago-Southland a reading of 46.5 points. Above 50 shows expansion, and below 50 contraction.
Otago Southland Employers Association chief executive John Scandrett had warned the previous month's buoyant 62.6-point reading should be viewed in a conservative light.
With the May outcome slipping back, the forecast had probably been correct, he said yesterday.
However, it was pleasing to again see there were positive construction signals coming through, supporting the fact that Christchurch rebuilding activity was "slowly but surely under way", and that selected local parties did have an involvement.
"This does not mean however that all regional construction activities are firing as expected, and there are survey comments that bemoan a sluggishness in our own Otago-Southland building performance levels."
Negativity continued to be seen in parts of the tourist sector.
"One could adopt the view that it is to be expected in what is a shoulder-season period for that industry, and that with the winter weather now kicking in, the anticipated new tourist flows will soon be evident," Mr Scandrett said.
He expected a similar to slightly improved outcome for the June PSI.
