Detry, who is enjoying his week away home where the winter conditions are harsh, sprinted towards the turn with three birdies on holes 10, 13 and 16 in his front nine.
The Belgian then continued his birdie blitz on holes 1, 3, 6, 7 and 9 to return with a bogey-free 63 for a one-shot lead over Thailand's Settee Prakongvech at the Phoenix Gold Golf and Country Club in Pattaya.
"It's beautiful to be here in Thailand as the weather's pretty horrible back home. It gets dark at 3.30 in the afternoon and the sun is up at 10 and we get so much rain and wind," said Detry.
"I'm not getting ahead of myself as there are still three more rounds to go and there are lots of good players here. The strength of the field is good and I just have to stay patient. And if I keep playing like that for the next three days, I'll have a good chance."
Settee, who is currently in 93rd place on the Order of Merit, knows he needs a very good result to move inside the top-61 place and secure his card for next season.
It is the last chance saloon for the 25-year-old as he is determined to close the year with a grandstand finish in front of his friends and family.
"It was a good round. I hit the ball really well and putted well," said Settee.
"I know this is my last chance to secure my Asian Tour card and I hope something good will come my way this week. I need a really big finish, maybe finishing inside the top three or win. But anything can happen in golf and I'm hopeful of miracles."
American Berry Henson signed for a 65 to restore some much needed confidence after securing only one top-10 this year in South Korea.
Henson mixed his card with seven birdies and one bogey to stay two shots back of Detry together with Thailand's Gunn Charoenkul in tied-third place.
Thailand's Phachara Khongwatmai, who is chasing his Asian Tour breakthrough this week, posted a 66, trailing Detry by three shots in a share of fourth place which also included Indonesia's Rory Hie.