World champion Mark Selby loses to Thepchaiya Un-Nooh at World Open

Un-Nooh moved 2-0 ahead boosted by a run of 64. Selby recovered to restore parity at 2-2, but the Thai player won three of the next four frames - including a rapid break of 91 in the seventh frame - to complete a 5-3 success.

“The first few frames I had to stay focused and just think shot by shot. But when he came back to 2-2, I thought the game was gone,” said Thepchaiya.

“After the interval I started focusing again and that made me play really well.”

A day of shocks also saw Crucible runner-up Ding Junhui crash out on home soil 5-1 to Leicester's Ben Woollaston, while pre-tournament favourite Judd Trump was sent packing 5-2 by China's Zhang Anda.

Four-time world champion John Higgins came through a tight encounter with Michael Holt 5-4, while there were comfortable wins for Shaun Murphy, 5-0 over Jimmy Robertson, and Neil Robertson who beat Thor Chuan Leong 5-1.

Mark Williams edged out Graeme Dott 5-4 as Ryan Day beat Barry Hawkins by the same score

John Higgins was a 5-4 winner over Michael Holt, who lost the final two frames in a match in which he pieced together four breaks of 50 plus.

2015 world champion Stuart Bingham lost 5-3 to fellow Essex potter Ali Carter while World Championship semi-finalist Alan McManus compiled runs of 69,100 and 64 in winning five straight frames in downing Liang Wenbo 5-2.

Shaun Murphy (Eng) 5-0 Jimmy Robertson (Eng)

Ben Woollaston (Eng) 5-1 Ding Junhui (Chn)

Neil Robertson (Aus) 5-1 Thor Chuan Leong (Chn)

Zhang Anda (Chn) 5-2 Judd Trump (Eng)

Kyren Wilson (Eng) 0-5 Daniel Wells (Eng)

Graeme Dott (Sco) 4-5 Mark Williams (Wal)

Ricky Walden (Eng) 1-5 Anthony McGill (Sco)

Xiao Guodong (Chn) 0-5 Kurt Maflin (Nor)

Tom Ford (Eng) 2-5 Joe Perry (Eng)

Barry Hawkins (Eng) 4-5 Ryan Day (Wal)

David Gilbert (Eng) 5-2 Zhou Yuelong (Chn)

Stuart Bingham (Eng) 3-5 Ali Carter (Eng)

Michael Holt (Eng) 4-5 John Higgins (Sco)

Alan McManus (Sco) 5-2 Liang Wenbo (Chn)

Thepchaiya Un-Nooh (Tha) 5-3 Mark Selby (Eng)