The 52-year-old will fill the vacancy left by former incumbent Peter Reid, who departed by mutual consent 12 months into a four-year contract to take up the post of assistant manager at Stoke after being told he could not split his time between England and the south-east Asian nation.
Robson's immediate task in his first foray into international management will be to build on the good work done previously by Reid and guide the nation to a place in the Asian Cup finals in Qatar in 2011, with Thai FA chief Worawi Makudi also targeting a place at the 2014 World Cup.
"He's agreed to become coach, he's very happy with what we've offered him," Worawi told reporters.
"It's a four-year deal. The plan is he'll coach Thailand for the Asian Cup, the Olympics and hopefully the World Cup, too."
Robson's previous managerial experience has included spells at Middlesbrough, Sheffield United, Bradford and West Brom.
It remains unclear how much time he will spend in the country and whether he will continue his role as global ambassador for former club Manchester United.
Thailand are currently third in Asian Cup Qualifying Group E with two points from two games following draws with Jordan and Iran.
