India's top singles player, ranked 90th in the world, overcame the challenge of his 199th-ranked opponent 6-2 2-6 6-4 in one hour and 43 minutes. (Agencies)
His next rival is Germany's Jan-Lennard Struff, who dumped top seed Mikhail Kukushkin 7-6 (6) 6-2.
Somdev raced to a 4-1 lead after breaking his rival twice in the opening set. The only blemish was facing a breakpoint in the sixth game but he saved that with an ace and served out the set in the eighth game.
However, he did not get a good start in the second set as he got broken in the second game and was down 0-3. Desein went with the momentum and kept consolidating his lead and broke the Indian in the eighth game to make it one-all.
Somdev got start he needed in the final set as he broke the Belgian in the first game but let go advantage by dropping his serve in the second.
India's Leander Paes and Rohan Bopanna are competing in the doubles main draw. Paes and his Czech partner Radek Stepanek have been seeded second and their first round opponents are Julien Benneteau and Edouard Roger-Vasselin from France.
Bopanna and his Pakistani partner Aisam-ul-haq Qureshi have been seeded third and they will open their campaign against Dutch player Jean-Julien Rojer and Horia Tecau from Romania.
The tournament is last ATP event before the Australian Open, season's first Grand Slam, starting January 13 in Melbourne.
India's top singles player, ranked 90th in the world, overcame the challenge of his 199th-ranked opponent 6-2 2-6 6-4 in one hour and 43 minutes.