O'Sullivan has been out of form and suffering from a wrist injury

It continued an erratic run of form by O'Sullivan since October, on which he has reached the Masters final but also suffered three first round defeats.

"I enjoy coming here and wanted to stick around longer but I couldn't make a 20 break," said O'Sullivan.

World champion Shaun Murphy also made a shock first-round exit, going down 5-2 to Michael Holt.

O'Sullivan has now gone five months without winning a match in a ranking tournament and will probably have to win next month's World Championship to avoid losing his number one status.

"Ranking tournaments are very important because I don't want to give up the number one spot but it looks like it's gone now," he said.

I was so tired that at one stage I wanted to leave Shaun Murphy

"I'm very disappointed to have come here and lost. I'll take nothing away from James because he played really well."

Wattana said: "I don't think Ronnie was in the right frame of mind and that gave me an advantage.

"It didn't look like his concentration was there. He seemed a bit lost."

John Higgins narrowly avoided following Murphy and O'Sullivan home, fighting back to beat Stuart Bingham 5-4.

Murphy, who has never travelled further than Malta for a tournament, said the long journey had affected his game.

"I was so tired that at one stage I wanted to leave. I've been waking up in the middle of the night and I am absolutely knackered," he said.

Higgins had to claw his way back against Bingham, who led 4-3 and was 63-11 up in the eighth frame.

But a kick caused a vital red to go astray, allowing Higgins to make a 53 clearance to stay in the game.

"I was thinking about going home," Higgins admitted afterwards.

"I thought Stuart would pot that black all day long. Missing it was a godsend for me and I made the most of it."

Higgins' next opponent is Peter Ebdon, who scraped past Mark Selby 5-4, and world number 14 Joe Perry battled back from 4-1 down to beat Adrian Gunnell by the same score.

Stoke's Jamie Cope came close to a 147 in his 5-2 win over Alan McManus, only coming unstuck when he missed the 15th red in the fourth frame.

"I was moving all over the place on the red," said Cope. "At the start of the match I couldn't settle at all but I played all right at the end."

Ricky Walden, who reached the last eight in this tournament last year, beat world number three Stephen Maguire 5-3, and after four fruitless visits to the country, Graeme Dott finally broke his duck in China.

His 5-1 win over Yu De Lu set up a second-round match with defending champion Ding Junhui.