Purdy, ahead by five strokes at the start of the day, and Lin Keng-chi of Taiwan (65) are at 14-under-par 199. Thais Thongchai Jaidee (65) and Thammanoon Srirot (65) are at 200.
Purdy's triple-bogey came on the eighth hole, where he hooked a 4-iron out of bounds.
'I left a lot of putts short, which I think was to do with nerves,' he said. 'I was happier with a five-shot lead but I am still happy to have a chance.'
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