He also captained Belgium at youth level.
An eyewitness told local media parts of the bodies turned blue, believed to be bruising from the impact of the strike.
"They were finishing their session and sitting up on their boards. Both men fell off their boards and sank into the water," he said.
Indonesian police spokesman Johannes H. Widya Nainggolan said the men "died on the spot".
Media reports indicate the men were taken to hospital where they were unable to be revived.
A number of Dasoul's former clubs came out on social media to post tributes, including Italian club Torres Sassari, which stated: "A tragic accident took away a loved one, Denis Andre Dasoul, who was only 34 years old.
"Denis served for Torres in 2010 and 2011 and we are reminded of the great human he was and his professional qualities. To his family we send our most heartfelt condolences from the Torres Sassari club."
Journalist Pascal Scime, a friend of Dasoul's, said the incident was a "tragedy" on Twitter.
"Denis was a marvellous person who lived every day like it was the last. He was always smiling and joking. A very nice guy. He was in Bali for holidays with his girlfriend," he said.