The Englishman is looking to overcome the disappointment of 2024, when a bogey on No.18 at Hong Kong Golf Club knocked him out of a three-man play-off, which was eventually won by Mexico's Abraham Ancer.
Chasing Casey is a pack of six players, all two shots back after rounds of 65 - Spaniards Sergio Garcia and Luis Masaveu, Colombia's Sebastian Munoz, Germany's Martin Kaymer, American Peter Uihlein and Taiwan wildcard Chieh-Po Lee.
A group of six more stands another shot back at four-under, including Bryson DeChambeau, while the top Australian is Lucas Herbert, a shot further adrift after his 67, which would have been better if not for a bogey at the 18th.
"I've always been a global traveller and enjoyed the challenge of trying to tick another country off on the win list," the 47-year-old Casey said, as he sought his first win in Hong Kong.
"It's something that always kind of excited me, to win around golf courses with history that are iconic. So, you can be assured that I'm trying very hard this week because I'd love to add this one to the list."
Driven by Casey and DeChambeau, defending champion Crushers GC took the team co-lead at 12 under with Torque GC.
The all-Australian Ripper GC were in eighth place, with Herbert's 67 backed up by 69s from Cameron Smith and Matt Jones, and 70 from Marc Leishman.
11°C