Buriram's Brazilian striker Guilherme Bissoli opened the scoring in the 30th minute at Gosford, north of Sydney, poking home Dion Cool's cross from the right-hand flank.
It was an Australian, Curtis Good, who added the second after 50 minutes.
The central defender, who was once on Newcastle United's books in the English Premier League, rose unmarked to head home Goran Causic's cross.
It got worse for the Mariners seven minutes later as goalkeeper Adam Pavlesic was given a straight red card when he raced from his area to scythe down Bissoli, who had beaten the offside trap.
The A-League team did get a consolation in the fifth minute of injury time, Lucas Mauragis firing home a sweet strike from outside the box but it was too little too late.
Buriram remain unbeaten after two rounds of the rebranded Asian Champions League after a goalless draw at home to Japan's Vissel Kobe on match day one.
Central Coast, who lost 3-1 at China's Shandong Taishan in week one, are bottom of the 12-team East Zone league table.
