It will be a meeting between the two fastest players on the circuit - O’Sullivan is dubbed the ‘Rocket’ and Thepchaiya ‘F1’.
The 32-player event at the Crucible Theatre in Sheffield, England, starts tomorrow and ends on Aug 16.
World No.6 O’Sullivan and No.20 Thepchaiya begin play on Sunday.
The 2020 championship was originally scheduled to take place from April 18-May 4 but was postponed due to the COVID-19 pandemic.
The tournament will allow a limited number of spectators and O’Sullivan is not happy with the decision.
“You aren’t really achieving anything. Having people there but not enough people doesn’t look good. Either pack it out and say we don’t actually care or go ‘we aren’t having anyone’,” the 44-year-old Englishman said last week.
Thepchaiya, 36, has won only one ranking tournament - the 2019 Shoot Out. He also won the 2015 Six-red World Championship in Bangkok.
Noppon Saengkham, the other Thai in the 2020 world championship, faces 2005 world champion Shaun Murphy of England.
World No.1 Judd Trump of England begins the defence of his Crucible title against compatriot Tom Ford tomorrow.