Jaidee shot a 5-under 67 in his second round and is 8 under overall at Pinx Golf Club.
He is joined by Goya, who carded a 70 after completing his first round earlier in the day with a 66. Goya birdied the final three holes in his morning round to give him momentum going into the afternoon session.
"The three birdies gave me a lot of confidence," Goya said. "It's easier finishing like that."
Both players began their second day of play early Friday after Thursday's first round was delayed by over six hours due to dense fog. As a result, organizers have reduced the event to 54 holes.
The third and final round will be played on Sunday, with two-thirds of the field having to complete their second rounds by Saturday afternoon.
They include first-round leader Marcus Fraser of Australia, who is one stroke off the lead, along with third-ranked Ernie Els and American Anthony Kim, who are in a group sharing 11th place at 4 under.
Fellow Australian Brett Rumford is tied with Fraser after completing his second round late Friday with a 70 that included three birdies and one bogey.
Local favorite Y.E. Yang of South Korea is on the verge of missing the cut at 6 over. This is his first competition in front of his hometown fans since winning the PGA Championships last year.
The $2.9 million Ballantine's Championship is an official European Tour event, co-sanctioned by the Asian Tour and the Korea PGA.