Advani, who won the billiards singles gold in Asian Games last month, failed to lift the coveted trophy that he last won in 2003 in China, after he lost 7-10 in the best-of-19 frames final, divided into two sessions.
Advani lost 37-67, 71-47, 69-35, 138-00, 12-85, 15-68, 13-63, 27-68, 57-56, 61-15, 15-71, 35-75, 32-58, 71-25, 62-33, 00-130, 08-92.
In the first session of the final, the Thai cueist led 5-4 and in the second, he stretched his lead to 10-7 to seal the issue in his favour beyond doubt. The seven times world champion Advani fought like a terrier to overcome severe pressure from the Thai opponent but in the end his efforts proved short of adding another milestone to his already illustrious career.
The final was a gruelling affair as Dechawat won the first frame with ease but Advani bounced back to draw even in the second. He then went on to win the next two frames, constructing a century break of 138 in the fourth.
The Thai opponent then reigned supreme on the green baize and won next four frames, reducing Advani to a mere spectator. The Indian then clawed his way back, winning the 9th and 10th frame to lock the issue at 5-5.
From there on, the Thai opponent raised the level of his game and added another three to his name, making it tough for Advani to make a comeback. Under pressure, Advani wilted in the end and only managed to win one more frame before Dechawat sealed the issue with a century break of 130 in the 16th and 92 in the 17th frame.
Meanwhile, in the 3rd-4th placing match, Rodney Goggins of Ireland defeated Noppadol Sangnil of Thailand 4-2.
Advani had defeated Goggins 7-4 in the first semi-final of the event yesterday, while Dechawat ended the challenge of Sangnil 7-5 in a keenly contested other last-four match.
The 25-year-old Bangalorean had topped Group E by winning all six matches and then got the better of Mohammed Joaker of the UAE 5-4 in the round of 32 match.
In the quarterfinal, he had crushed Moh Keen Hoo of Malaysia 6-1 in the best-of-11 frame contest.
In the women's event, Ng On Yee of Hong Kong beat countrymate Jaique Ip Wan 5-0 in the best-of-9 frames final. Phil Williams of Wales emerged victorious in the Masters category, defeating Chuchart T of Thailand 6-4 in the best-of-11 frames final.