
Boonsak, ranked No 11 in the world and runner-up at last month's Thailand Open Gold Grand Prix, packed up his bag after losing 21-18 14-21 14-21 to Jan O Jorgensen, who is ranked 20th in the world and was a winner at the Swedish International Tournament in January.
Earlier, team-mate Tanongsak Saensomboonsuk lost 16-21 12-21 to Beijing Olympics champion Lin Dan of China in a late second-round match on Wednesday night.
Boonsak's younger sister Salakjit found former world and All-England champion Xie Xingfan too strong, losing the three-game battle 16-21 21-14 9-21 in 51 minutes in the women's singles third round yesterday.