Three-time major winner Ernie Els only managed even par in humid conditions on the 7,169-yard, par-71 Serapong course, where temperatures reached 86 degrees.
'The heat was really a factor, especially after my start,' Els said. 'I hit a lot of quality golf shots on the back nine but could not buy a putt. It was very frustrating as I hit the ball very nice.'
Defending champion Adam Scott of Australia was three shots off the pace after a 1-under 70.
Former U.S. Open winner Michael Campbell of New Zealand, teeing off from the back nine, followed an eagle on the third hole with a double bogey on the par-4 fourth en route to a 1-over 72.
Strange, who won this year's Philippine Open, overcame two early bogeys and had six birdies for his share of the lead, while Pagunsan put together an mistake-free round with four birdies.
India's Jyoti Randhawa is third after shooting a 68, one better than Japan's Shingo Katayama, Argentine Angel Cabrera, Australians Scott Barr and Nick O'Hern and South African amateur Christopher Joseph.
Els, looking for his first win of the year, double bogeyed the second and had another bogey on the third on his way to a share of 18th place.
But he believes he can overcome his slow start.
'It's the first round and you do not win a tournament on the first day,' Els said. 'I just need to get into position by hitting quality golf shots.'
England's Lee Westwood, who had three bogeys and a double bogey, is six strokes behind the leader, while Ryder Cup teammate Paul McGinley of Ireland is in danger of missing the cut after a 5-over 76.
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