Lahiri, who was briefly in joint lead, ended four shots behind the co-leaders Lee Westwood and Graeme McDowell, who shots six-under 66 each.
Lahiri was the best Indian on a day when most of his colleagues played way below their best. Shiv Kapur (72) was tied 40th, Rashid Khan and Jeev Milkha Singh carded 73 to be tied 58th and Gaganjeet Bhullar (74) was 78th. SSP Chowrasia and Arjun Atwal carded 76 each to be 103rd, Rahil Gangjee shot 77 and Jyoti Randhawa 78.
"I'm quite disappointed. It is not often that you should two-under on this golf course and you feel bad. It was disaster coming in because I played really good. One bad shot and I lost my focussed and could not hole any putts," said Lahiri, who started from tenth and birdied the 10th, 12th, 14th, second and third to go to five-under.
Speaking of his rough patch, he said, "I hit it into the greenside trap on the par five sixth hole. Hit a bad bunker shot and got unlucky because the ball kicked forward and went into the water. Oh the next hole, I made a bad swing and missed a short putt."
Five players, including Prom Meesawat, carded 68 each.