Sussex's Davis took the top prize of two million Baht (around £40,000) at the Montien Riverside Hotel with a fine display in the final against world number one Robertson. Davis has dominated recent tournaments with the six-red format as he also took the title at one in Ireland in 2009.
Robertson led 3-1 before Davis won six frames in a row, before claiming victory in the 12th.
The 41-year-old world number 17 said: "There was no real pressure on me going into the match. I got a bit nervous in the last frame, but then got the chance I had been looking for. It was my safety that really worked well today and I am happy to have the claimed the title again.
"I know I'm out of the top 16 now, but I'm not worried as it is only the beginning of the season. I am enjoying my snooker and that is the most important thing."
Final result: Mark Davis beat Neil Robertson 8-4 (0-75, 37-3, 1-42, 6-74, 66-0, 37-21, 58-1, 39-7, 43-0, 78-0, 0-77, 63-15)