The motive remains unclear, but Mr. Koh had been threatened several years earlier for preaching in settings where Muslims could be swayed. It is illegal in Malaysia to try to convert Muslims to Christianity.
Three other disappearances since late 2016 also involve victims who challenged the prevalent Malaysian view of Islam.
Pastor Joshua Hilmy, a convert to Christianity from Islam who was known to preach his new religion freely, disappeared around Nov. 30, 2016, along with his wife, Ruth Sitepu. They packed no belongings and their car is missing.
A week earlier, Amri Che Mat, who was said to promote a Shia interpretation of Islam in this predominantly Sunni nation, disappeared as he was driving near his home in Perlis, Malaysia’s northernmost state.
Just before midnight on Nov. 24, 2016, four-wheel-drive vehicles surrounded his car, a witness said. He car was later found abandoned. Mr. Amri, the founder of a charity group called Perlis Hope, has not been heard from since.
Earlier this month, a police officer came forward and told Mr. Amri’s wife, Norhayati Mohamed Ariffin, that a team of police officers had kidnapped her husband and Mr. Koh.