The cabinet will be asked this month to approve two new train route extensions in the North and Northeast worth a combined 153 billion baht.
The routes in question are: Den Chai-Chiang Rai-Chiang Khong in the upper North and the Ban Phai-Mukdahan-Nakhon Phanom in the upper Northeast.
The former route will branch out from the main northern line in Phrae and the latter will fork off from the upper northern line in Khon Kaen.
Transport minister Saksayam Chidchob said the 326km Den Chai route will cost 85 billion baht and the 355km Ban Phai route will have a price tag of 68 billion baht.
He said the ministry would forward the two projects to the cabinet for approval this month. If they get the go-ahead, the first step will be the issuing of a royal decree to expropriate the land needed.
Saksayam also gave an update on the building of the Bang Sue-Rangsit Red Line extension in northern Bangkok, saying the State Railway of Thailand (SRT) estimated the project to be over budget by at least 10.3 billion baht.
He said the cost had blown out because the design did not correspond precisely to the actual cost of construction and the prices of the three winning contracts were approved above the predicted price.
The Red Line extension had already exceeded the approved budget of 55 billion baht. It had been revised up to 93 billion baht and will now be pushed up by a further 10.3 billion.
The minister said the elevated extension was the fifth and final section of the Red Line, which will run from Taling Chan to Rangsit.
Saksayam said the government had a limited budget for investing in the project.
The ministry thought it best to adopt a public-private partnership by granting contractors the right to operate trains under a 30-year concessionary deal.