The cabinet on Tuesday approved a 111-billion-baht project to build two new rail lines in Bangkok, part of a wider infrastructure push by the government as it seeks to boost a sluggish economy.
Transport Minister Arkhom Termpittayapaisith said the cabinet approved construction of a Pink Line and a Yellow Line.
"We'll now look at the bidding process to ensure it takes place within the next three months," Mr Arkhom told Reuters.
The rail lines are part of the government's infrastructure drive, aimed at kick-starting Southeast Asia's second-largest economy.
The Bank of Thailand on March 23 cut its 2016 growth forecast to 3.1%, as the economy was losing steam and still faces global risks.
The government has said the rail links are needed to reduce traffic congestion in Bangkok, which currently has three skytrain lines and one underground line.
The 34.5-kilometre Pink Line will run from Bangkok to Nonthaburi province. The 30.4-kilometre Yellow Line will run from Bangkok to Samut Prakan province.
Their construction will be funded on a public-private partnership basis.