Prom Meesawat of Thailand was a stroke back at 5 under at the Thai Country Club.
Kapur had eight birdies and two bogeys. Buckle, who arrived in Thailand on Wednesday and didn't even have a chance to check out the course before going straight into Thursday's first round, made six birdies and no bogeys.
'It was my first time playing on this course, which made a bit easier. I just went out there and played well,' said Buckle, who didn't bring his own caddie and is using the services of a local female caddy who gave him tips on playing the course.
Four players were tied for fourth at 68, including Thailand's Thammanoon Srirot, who had an eagle on the seventh hole. Thammanoon was joined by Ted Ho of South Korea, Anthony Hang of the United States and Adam Fraser of Australia at 4 under.
Defending champion Jyoti Randhawa of India kept himself in contention with a 2-under 70.
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