Singh, who came face-to-face with Obama on three occasions for the first time after he was re-elected President in the November 6 polls in the US, told him: "Congratulations on your re-election."
The two leaders, who attended the East Asia Summit and the retreat in the Cambodian capital, shook hands and exchanged pleasantries.
51-year-old Democrat Obama had defeated his Republican rival Mitt Romney in the Presidential polls to secure a second four-year term.
After Obama's re-election, Singh had said he looked forward to continuing their "friendship" and "rewarding association" as much more can be done together to further strengthen the bilateral partnership.
In his congratulatory message to Obama, Singh had referred to the association between the two leaders over the past four years and recalled that cooperation between the two countries had not only been advanced across the full spectrum of ties but engagement had been deepened.
"Dear Mr President, it gives me great pleasure to convey to you my warmest congratulations on your re-election as the President of the United States," Singh's letter had said.
Meanwhile, national security adviser Shivshankar Menon held a 90-minute meeting with his US counterpart Tom Donilon here and discussed bilateral relations and other issues of mutual interest.
Sources said it was a very fruitful interaction on several issues of mutual interest.