The sandals of the Prophet (ﷺ) had two thongs.
Sunan Abi Dawud Book 34, Hadith 115
← Previous Hadith We were with the Prophet (ﷺ) on a journey. He said: Make a general practice of wearing sandals, for a man keeps riding as long as he wears sandals.

Sunan Abi Dawud Book 34, Hadith 114 Next Hadith → The Messenger of Allah (ﷺ) forbade that a man should put on sandals while standing.

Sunan Abi Dawud Book 34, Hadith 116