Khun Mang, 35, pulled up alongside a vehicle driven by Druman Jipapan, about 45, and fired several shots, one of which hit Khun Druman in the neck.
Khun Druman, a Phuket Prison guard moonlighting in a second job, was carrying three million baht to a meeting. It is believed the money was a pay-off to a high-ranking official to settle a case involving drugs.
A warrant has now been issued for Khun Mang, who escaped. Khun Druman underwent surgery at Vachira Phuket Hospital in Phuket City and is recovering.
The shooting began close to Chalong temple and continued as both vehicles travelled side by side down Chao Fa Road East and ended when Khun Druman stopped outside a relative's house near Phuket Zoo.