Joshi, who had rounds of 66-73-70-72 totalled seven-under 281 and picked up USD 4266.
Thai teenager Rattanon Wanasrichan saved his best for last when he fired a seven-under-par 65 to win his first Asian Development Tour (ADT) title.
Rattanon, 20, shot eight birdies to return with a winning total of 12-under-par 276 to defeat a battling Casey O'Toole (66) of the United States and overnight leader Jordan Sherratt (71) of Australia by one shot.
Rattanon, who was five shots back at the start of the day, got off to a hot start when he opened with three birdies. He added three more birdies in the middle of the round and sealed the deal with two closing birdies.
He said, "I told myself that if I can birdie the last hole then I can win. I managed to do that so I am proud of myself. I was five shots back after round three so I didn't think I can win. I just played my own game and I am glad that I won."
O'Toole continued his good run of form on the ADT after claiming his seventh top-10 result.
Australia's Sherratt missed a 10-foot birdie putt on the last hole to force a play-off and was disappointed not to win his career's first title after leading for two days.
