O'Sullivan heaped praise on Wattana, a trailblazing figure for Asian players in the game who won three ranking tournaments and reached the World Championship semi-finals twice.
Recalling his first meeting with Wattana in Thailand in 1993, O'Sullivan said: "I played James out here when he was at his peak and was in his prime.
"I played him in a match and we had to stop for the adverts. He was in them all - Nescafe and Thai Airways. I was sitting there thinking, this geezer is unbelievable."
"When he was in his prime, he couldn't go anywhere. He needed security and a police escort. He has been massive for Thai snooker."
Wattana will face China's Zhang Anda in the last 16 of the competition while O'Sullivan will take on Ding Junhui.
Mark Williams secured the two wins he needed to reach the last 16 where he will now face Judd Trump, who finished top of Group D after a 5-4 win over Mai Hai Long.
