Brosque lashed home a left foot strike from inside the penalty area to complete the comeback after Thai defender Chonlatit Jantakam slipped as the ball bounced to the Australian striker.
The result and three points gave Australia an early lead in Group D with Oman hosting Frank Rijkaard's Saudi Arabia later on Friday in the other match in the group.
Although the Socceroos dominated possession they failed to create the chances they should have in a rusty performance in front of 24,540 fans.
The Thais took a surprise lead in the 14th minute after a quick break from their own half when Neil Kilkenny gave the ball away.
Midfielder Matt McKay, playing out of position at left-back, was exposed as the visitors broke down their right and a pinpoint cross from Jakkaphan Kaewprom cut out Australian captain Lucas Neill.
Teerasil Dangda was on hand to cushion the ball past a helpless Mark Schwarzer.
Australia, ranked 22 by FIFA and some 98 places ahead of Thailand, improved their intensity after the break and equalised in the 58th minute through Japan-based striker Josh Kennedy.
McKay made up for his earlier error by firing a left-foot shot which goalkeeper Sinthaweechai Hathairattankool could only parry to the feet of Kennedy who easily converted to equalise.
Thailand, who narrowly edged Palestine 3-2 on aggregate in the previous round, were marshalled superbly by defender Niweat Siriwong as they battled to hold the mighty Australians at bay.
But Chonlatit's late slip allowed Brosque the space to fire the winner as Australia coach Holger Osieck was able to celebrate victory over his compatriot, Thailand boss Winfried Schaefer.
Australia travel to the Middle East to play Saudi Arabia on Tuesday with Thailand hosting Oman.
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