Lalang, who won the Commonwealth title in New Delhi two years ago, finished behind the qualifiers for Saturday's final in his heat won by world record holder Rudisha in 1:44.0.
"I am happy to have passed this hurdle. Now I am focusing on the final on Saturday," Rudisha said.
Olympic 1,500 champion Asbel Kiprop and world silver medalist Silas Kiplagat also made it to the final, with Kiprop winning his semi-final in 3:49.1.
Kiplagat was second in the second semi-final behind Nixon Chepseba.