After world No 1 Judd Trump bowed out of the tournament on Monday, O’Sullivan was looking to avoid an upset when resuming his bid for a record-breaking 37th ranking title.
And the defending champion in York safely reached the fourth round with a 6-2 victory over world No 32 Saengkham.
'Only Ronnie would take that plant on!' Watch O'Sullivan sink audacious shot
O’Sullivan took the opener before losing his first frame of the tournament as Saengkham levelled up.
Saengkham was gutsy with his shot-choices but ultimately paid the price as O’Sullivan led 3-1 at the interval.
The Noppon Saengkham fluke that left Ronnie O’Sullivan cracking up
O’Sullivan moved within a frame of victory at 5-2 thanks to a break of 97, and closed out the match when winning a tight eighth frame.
Speaking after his victory, O'Sullivan told Eurosport:
I'm pleased to get through. The table was playing really hard and tight and heavy, it was hard to control the white, but I thought I managed it pretty well.
"Flukes are all part of the game," O'Sullivan added, after a couple of lucky breaks for Saengkham. "He's the king of the flukes today, I want to buy those flukes off of him."
Hobbling O'Sullivan in fine form after win over 'King of the flukes' Noppon Saengkham
In the other featured match of the afternoon session, Ding edged out Ali Carter 6-4, taking the last frame with a break of a match-high of 116 to secure victory.
Mark Selby inched past Martin O'Donnell in a slow-tempo match in the evening session, while Yan Bingtao made it another disappointing tournament for the frustratingly talented Jack Lisowski.
In-form Gary Wilson looks a dangerous proposition, with his 6-1 win over Joe Perry being the most convincing of the day at the Barbican.
Michael White 6-5 Mark Davis
Mark Selby 6-3 Martin O'Donnell
Yan Bingtao 6-3 Jack Lizowski
Gary Wilson 6-1 Joe Perry
Liang Wenbo 6-4 Eden Sharav
Ding Junhui 6-4 Ali Carter
Stephen Maguire 6-2 Graeme Dott
Ronnie O'Sullivan 6-2 Noppon Saengkham