Selby has made a slow start to the season after recovering from an injured toe following his third world title success in May.
He has yet to go beyond the last 16 of any tournament so far this season, but showed he has lost none of his confidence as breaks of 65, 95, 86, 57 and 58 proved too much for the Thai player, who had led 2-1 boosted by runs of 53 and 72.
“I didn’t start off very well and probably should have been 3-1 down at the interval,” said Selby, who meets fellow Englishman Lee Walker in the last 64.
World Open
Carter whitewashes Higgins to reach World Open semi-finals
29/07/2016 AT 08:30
“After the break I thought I played a bit better, but I will need to improve as the tournament goes on.”
There was also a 5-1 win for home favourite and world number four Ding Junhui against Hammad Miah in a match held over from qualifying for the fifth ranking event of the season.
Former UK and Masters champion Ding will meet Zhang Anda in the first round.
Mark Williams completed a 5-0 win over fellow Welshman Matthew Stevens, who was forced to play with a borrowed cue due to lost luggage via the UK.
Former world champion Williams finished with breaks of 126 and 64 to reach the last 32 and a meeting with Mark King or Chez Zhe.
World Open
Higgins ousts Williams to reach World Open quarter-finals
28/07/2016 AT 15:52
World Open
World champion Selby loses to Thepchaiya at World Open
27/07/2016 AT 13:51