The 18-year-old Sarawakian clocked a personal best time of 1:49.67 at the Bukit Jalil Aquatic Centre to erase fellow national swimmer Lim Ching Hwang’s time of 1:50.62 set last year.
Kevin Yeap Soon Choy of Perak clocked 1:52.59 to take the silver while Sarawak’s Vernon Lee grabbed the bronze with a time of 1:52.62.
“I trained hard for this event and was expecting to beat the national record. I swam well and I’m quite pleased with my efforts,” said Welson, the winner of the 100m freestyle on Thursday.
Welson will also attempt to win his third gold in the 400m freestyle event.