Kenyan duo of Abel Kirui (2:08.27) and Wilson Kipsang Kiprotich (2:09.37) bagged the silver and bronze respectively.
The 31-year-old Ram Singh, from the Army Sports Institute in Pune, clocked a slow 2 hours, 30 minutes and 19 seconds, a far cry from the best personal best time of 2:16.59 that he set up in the Mumbai Marathon in January to dip under the Olympic 'B' standard of 2:18.00.
Yadav, only the second Indian to take part in the gruelling race after Shivnath Singh's appearance in Olympics in 1976 at Montreal, was timed at 1:59.39 and 2:20.36 when he crossed the 35 and 40-km mark.
The experienced long distance runner had to prove his fitness for competing at the mega event by running a 10-km race in 32 minutes and 10 seconds on the synthetic track at Coimbatore five days before the Games opened here before he was cleared by the Athletics Federation of India to run here.
Varanasi-born Yadav was asked by the AFI to prove his fitness on the ground that he had not taken part in a competition for some time after qualifying for the Games.
As many as 20 runners failed to finish the gruelling race that commenced at 11 AM local time.