The California native carded a sizzling six-under-par 64 in round four to finish 20-under overall, holding off local favourite Matthew Cheung and Finland’s Kalle Samooja by five strokes.
Thailand’s Jazz Janewattananond and Nick Voke of New Zealand finished tied for fourth at 14-under.
It’s Catlin’s first triumph on the Asian circuit since the 2024 Saudi Open, and adds to victories in Thailand, Macau, and Malaysia.
Catlin went into the final round locked in a tense four-way tie for the lead at 14-under-par alongside compatriot Caleb Surratt, India’s Anirban Lahiri, and Thomas Pieters of Belgium.
But a brilliant performance on the 18th-hole sand solidified his place at the top of the leaderboard.
Victory in the SAR also came with another milestone for Catlin, who is ranked 447 in the world.
With the Asian Tour tournament a part of The Open Qualifying Series, his strong showing in Fanling earned him a highly coveted qualifying ticket to the 155th edition of the prestigious event, which will be played at the historic Old Course in St Andrews next July.