Prayad, the current leader of the ASEAN PGA Tour Order of Merit, shot a seven-under-par 65 while Prom returned an impressive 63.
The duo lead the event on 13-under-par at Royal Hua Hin Golf Club.
Thailand’s Kwanchai Tannin, the 2013 ASEAN PGA Merit list winner, and Pawin Ingkhapradit, are a shot further back following rounds of 69 and 65 respectively.
Their teenage compatriot Phachara Khongwatmai, winner of this event in 2013 as a 14-year-old amateur, is a stroke further back after shooting a 70.
Wolmer Murillo from Venezuela, the leader after the first two days, slipped back after firing a 74 and is nine under for the tournament in a tie for seventh.
Prayad claimed the Singha Pattaya Open in March, for the second successive year, to help place him at the top of the Merit list. He has currently earned US$15,255, with three events having been played so far this year.
He did not drop any shots today and made three birdies on the front nine and four coming home.
Prom also went bogey free and noticeably birdied his first three holes and later the first three holes on the back nine.
Defending champion Gunn Charoenkul from Thailand, winner of last year’s Merit list with three victories, came in with a 69 and has an outside chance as he is six behind the leaders.