The Thai player joined Stephen Hendry and John Parrott in making a surprise exit from the competition as Snaddon, the world No 74, beat him 5-3 to reach the last 16. Snaddon, from Sauchie, near Stirling, is now guaranteed pounds 5,500, more than twice as much as he earned in the whole of last season.
'I beat Alex Higgins in the qualifying rounds of this tournament, but I've got to count this as my best win ever,' Snaddon, Hendry's regular practice partner, said.
Snaddon, who took up snooker after a hip disease cut short a promising football career, took advantage of Wattana's many mistakes to establish a 4-0 interval lead with breaks of 46, 36, 80, and 60.
After the break, Wattana began to show the form which took him through to the semi-finals of the Dubai Classic a fortnight ago. He reeled off three successive frames in 34 minutes with rapid runs of 76, 73 and 59, and looked about to level at 4-4 when Snaddon presented him with another opening in the eighth.
He missed a simple blue to a middle pocket, however, and Snaddon, making his television debut, held his nerve to compile a 50 break. He potted the penultimate red from distance, killing off Wattana's comeback.
In the next round Snaddon meets the Dubliner ranked No 21 in the world, Ken Doherty, who beat Willie Thorne 5-2 in his fourth-round match.
Thorne, the world No 15, scored only 47 points in the opening four frames as Doherty registered breaks of 37, 64, 51 and 33. After the interval Thorne, who has risen to sixth on the latest provisional ranking list, rallied to 4-2 before Doherty's 52 break in the seventh frame proved decisive. .
Neal Foulds, the sixth seed and winner of the Regal Scottish Masters title last month, pulled away from a 2-2 interval deadlock to beat Nick Terry 5-2.
ROTHMANS GRAND PRIX (Hexagon Theatre, Reading) Fourth round: B Snaddon (Sco) bt J Wattana (Thai) 5-3; N Bond (Eng) bt B Oliver (Eng) 5-2; K Doherty (Irl) bt W Thorne (Eng)
5-2; N Foulds (Eng) bt N Terry (Eng) 5-2.Reuse content