World number one Mark Selby crashed out of the Hong Rui Ma Yushan World Open after he was beaten 5-4 by Noppon Saengkham.
The Thailand world number 53 had opened up an early 3-0 lead, before Selby mounted a recovery on the back of breaks of 102 and 50.
Saengkham then put himself within a frame of the quarter-finals, only for Selby to hang in and force a decider, which the Thai player edged 58-55 after both men had missed chances to seal victory.
World champion Mark Williams, though, had little trouble as he coasted to a 5-1 win over Joe Perry, the Welshman producing four half-century breaks.
Elsewhere in Thursday's morning matches, Jack Lisowski recovered from 3-0 down to edge out World Championship semi-finalist Kyren Wilson 5-4, potting a decisive pink right-handed, to secure a showdown against Williams.
Xiao Guodong knocked out Anthony Hamilton 5-3 and will meet Saengkham in the last eight.
World Open: Last 16 tournament bracket
Ties to be played Thursday
- Mark Selby 4-5 Noppon Saengkham
- Xiao Guodong 5-3 Anthony Hamilton
- Kyren Wilson 4-5 Jack Lisowski
- Joe Perry 1-5 Mark Williams
- Robert Milkins 2-5 Marco Fu
- David Gilbert 5-3 Ricky Walden
- Barry Hawkins 5-4 Matthew Selt
- Fergal O'Brien 2-5 Gary Wilson
Quarter-finals to be played Friday
- Noppon Saengkham v Xiao Guodong
- Jack Lisowski v Mark Williams
- Marco Fu v David Gilbert
- Barry Hawkins v Gary Wilson
Semi-finals to be played Saturday
Final on Sunday