The Malaysian swimmer clocked 1:48.47, just 0.53s behind Katsuhiro Matsumoto of Japan in Heat Four, which was enough for him to finish the overall fifth fastest swimmer, while fellow compatriot Keith Lim missed out on a place in the final with a time of 1:54:22.
China's Sun Yang, who won silver in the event four years ago, set the overall pace with a time of 1:47.58 in the fifth heat.
For the record, Sim's personal best as well as Malaysia's national record was 1:47.36, which was set in the men's 200m freestyle relay at the 2017 SEA Games.
As for other Malaysian swimmers competing on the same day, Phee Jinq En qualified for the women's 100m breaststroke final, while Tern Jian Han crashed out in the men's 100m backstroke heat.
The finals involving Sim and Phee will take place later today in the evening.
MEN'S 200M FREESTYLE HEAT RESULTS
1. Sun Yang (China) - 1:47.582. Khader Ghetrich Baqlah (Jordan) - 1:47.60
3. Katsuhiro Matsumoto (Japan) - 1:47.94
4. Naito Ehara (Japan) - 1:47.76
5. Welson Sim (Malaysia) - 1:48.47
6. Lee Hojoon (South Korea) - 1:48.49
7. Ji Xingjie (China) - 1:48.85
8. Hoang Quy Phuoc (Vietnam) - 1:49.68
R. Yeo Kai Quan (Singapore) - 1:50.39
R. Jang Donghyeok (South Korea) - 1:50.48
WOMEN'S 100M BREASTSTROKE HEAT RESULTS
1. Satomi Suzuki (Japan) - 1:06.922. Reona Aoki (Japan) - 1:07.24
3. Shi Jinglin (China) - 1:07.68
4. Jamie Yeung Zhen Mei (Hong Kong) - 1:07.86
5. Yu Jingyao (China) - 1:08.52
6. Kim Hyejin (South Korea) - 1:08.64
7. Phee Jinq En (Malaysia) - 1:08.83
8. Back Suyeon (South Korea) - 1:09.08
R. Lin Peiwun (Chinese Taipei) - 1:09.63
R. Anandia Evato (Indonesia) - 1:09.78
