Like Prom who posted a second round one-under-par 71, Karlberg also continued his stranglehold at the Asian Tour season-ending event by signing for a two-day total of eight-under-par 136 at the Black Mountain Golf Club, which is his home course.
42-year-old Mo Joong-kyung of Korea showed he is capable of matching his younger rivals stride for stride when he got back into the groove with a 68 to trail the leaders by one in third place.
Japan's Kodai Ichihara gave himself a glimmer of hope of saving his Tour card after a 68 gave him a share of fourth place alongside Australia's Adam Groom, Kieran Pratt, Chinese Taipei's Lin Wen-tang as well as Thailand's Chawalit Plaphol and Pavit Tangkamolprasert.
Despite dominating the King's Cup for two consecutive days, Prom knows he has to remain patient if he wants to end his eight-year title drought and make up for the heartbreak of losing in two play-offs in the Philippines and Hong Kong late last year.
"It's going to be a tough weekend as the door is still open for everyone. I just want to maintain my composure and get an under-par score for the next two days," said Prom.
Karlberg staged a late comeback with two birdies in his last three holes to deny home favourite Prom the outright lead.
The two-time Asian Tour winner struggled under gusty conditions and was two-over in his second round after 12 holes. However, a birdie on the 13th managed to restore some measure of confidence for the Swede.
"It was a horrible round for 12 holes. I really struggled. I didn't play well and the putts didn't fall," said Karlberg.
"But the wind came down the right way on 17 and 18 and I was glad I finished off well," added Karlberg.
Adam Groom and Kieran Pratt lead the Australians in a share of 4th position.
For Groom especially the weekend is an important stretch of golf. Groom is currently 60th on the money list and needs to be inside the top 60 to retain his playing privileges for the 2014 season. This week's event brings to a close the 2013 season. By making the cut he might well have done enough.
Marcus Both is 17th, Scott Hend 30th, Sam Brazel, Andrew Dodt, Darren Beck and Scott Barr 35th and Unho Park 47th.
Players such as Both, Brazel, Dodt and Beck need to take full advantage of the weekend otherwise they will be potentially off to Tour School although Jake Higginbottom, David Lutterus and Ryan McCarthy, who all missed the cut, will now likely be forced to return to Tour School.
Leading scores after round 2 of the King's Cup Golf Hua Hin being played at the par 72, 7386 Yards Black Mountain GC course (a- denotes amateur):
136 - Prom MEESAWAT (THA) 65-71, Rikard KARLBERG (SWE) 65-71.
137 - MO Joong-kyung (KOR) 69-68.
138 - Adam GROOM (AUS) 69-69, Kodai ICHIHARA (JPN) 70-68, Chawalit PLAPHOL (THA) 69-69, Kieran PRATT (AUS) 68-70, LIN Wen-tang (TPE) 66-72, Pavit TANGKAMOLPRASERT (THA) 69-69.
139 - Johan EDFORS (SWE) 70-69, Prayad MARKSAENG (THA) 68-71, HUNG Chien-yao (TPE) 72-67, Alex CEJKA (GER) 70-69.