The new Red Line electric train service between Bang Sue and Rangsit will open in November next year, government spokesman Anucha Buranachaisri said on Friday.
Test runs will begin in March, he said.
The Red Line, to be operated by the State Railway of Thaliand, will run for 21 kilometres from the new Bang Sue Grand Station to Rangsit in Pathum Thani. The train will travel at up to 120 kilometres per hour and the full trip will take 30 minutes .
At least 270,000 passengers are expected to use the train each day.
Bang Sue Grand Station will also be opened in November, Mr Anucha said.
Construction was almost complete. It will be the mass transit centre of Bangkok, linking mass transit train lines with inter-provincial trains and buses.
Prime Minister Prayut Chan-o-cha will inspect the progress of construction on Tuesday, the spokesman said.