Philippine President Rodrigo Duterte missed several meetings at a regional summit because he was taking "power naps", said the presidential office.
A spokesman said Mr Duterte missed four scheduled events on Wednesday because he was "catching up on sleep".
Mr Duterte and other world leaders are in Singapore attending the Association of South East Asian Nations (Asean) meeting.
The 73-year-old defended his actions, saying: "What's wrong with my nap?"
Mr Duterte has previously missed events at other international summits as well as in the Philippines. His health has been a constant source of speculation over the year, and he revealed in October that he had had a cancer scare.
'In top physical shape'
Spokesman Salvador Panelo said the president had "worked late and had only less than three hours of sleep".
When asked if he was fully rested, Mr Duterte added that the naps were "still not good enough, but enough to sustain the endurance for the last days".
Mr Panelo also clarified that Mr Duterte's absence had "nothing to do with his health".
"The president's constantly punishing work schedule is proof that he is in top physical shape," he said in a statement.
Mr Duterte has previously admitted that he is tired and ready to quit, but says he had not found a suitable successor yet.
But he wasn't the only official caught napping at this year's Asean meetings.
A Washington Post columnist captured a picture of South Korean president Moon Jae-in, in which he appeared to be asleep.
Josh Rogin later reported that Mr Moon "woke up from his nap" after US Vice-President Mike Pence arrived.
Bloomberg reporter Toluse Olorunnipa also reported that Mr Moon had fallen asleep after "waiting 15 minutes" for Mr Pence to arrive.
"Ah, there's my friend," @VP Pence says as he walked in to bilat with South Korean President Moon Jae-In. Moon, who had been waiting for 15 minutes, jolted awake from a quick nap when Pence walked in. #ASEAN #VPinAsia pic.twitter.com/Ui7JvLME8J— Toluse Olorunnipa (@ToluseO) November 15, 2018
Mr Duterte and Mr Moon are attending the annual Asean meeting alongside other world leaders including Chinese Premier Li Keqiang, Russian President Vladimir Putin and Japanese Prime Minister Shinzo Abe.
The meetings end on 15 November.