His colleague Jeev Milkha Singh (66-70) is two behind and in tied 16th place.
Chowrasia, one of the only three Indians to have won twice on the European Tour, had six birdies against one bogey in his 67 at the Castle Stuart Golf.
He is only two shots behind joint leaders Francesco Molinari (62-70) and Alexander Noren (66-66).
Thongchai Jaidee of Thailand, winner of the ISPS Handa Wales Open last month, who gave Chowrasia some valuable advise shot a 70 for equal 33rd place.
"It was very good, I changed my game plan because the last few weeks, we changed my irons, and so it's much better. This week, my putting is also very good," said the Indian.
"I asked Thongchai how he was playing and any mental tips. He said 'just hit it straight ball and green, two-putt, two-putt...The birdie will automatically come'," he added.
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With Stuart Castle being a typical Scottish links course, Chowrasia said he is feeling right at home.
"Normally I'm not used to playing links courses but I like links course, because I chip and roll, and really like it. This week I'm playing very good, so let's see." (MORE)