Paes, who had won the doubles title here on five occasions in the company of Mahesh Bhupathi, was partnering Vasselin for the first time and the Thai duo steamrolled the rival in the second set completely.
Vasselin was broken in the very first game and then Paes and his partner managed to return the compliment in the sixth game.
Then, the rivals won their respective games to meander the set to a tie break.
Here, the seeds trained 2-5 but Paes brought about parity to level the score at seven all before surrendering the initiative.
In the second, the Thai duo broke Paes in the fourth game after a one-all scoreline and then broke Vasselin in the sixth game, after which Sonchat held his serve for the set and the match.