MANILA — President Rodrigo Duterte of the Philippines joked on Monday about using marijuana to stay awake at official functions, but the punch line appeared lost on a nation where thousands of people have been killed in his antidrug campaign.

At a ceremony meant to honor diplomats and employees of the Department of Foreign Affairs, Mr. Duterte said that the Association of Southeast Asian Nations, a regional group known as Asean that includes the Philippines, had a grueling meeting schedule. It was an apparent reference to local news reports that he had missed events at the Asean summit meeting in Singapore last month so he could take “power naps.”

Mr. Duterte, 73, said that attendance at some meetings should be delegated to the “lower echelons” or ministerial staff, and that leaders should tackle only the “most important ones.”

He said that on a recent trip to India, he had stayed up all night because he wanted to catch up on documents, “and the more that the crescendo becomes faster, the more you can’t sleep because you’re catching up on reading.”