The Transport Ministry is looking at the possibility of handing the entire Green Line train project to the Bangkok Metropolitan Administration (BMA).
Transport Minister ACM Prajin Juntong said on Monday the BMA had agreed to take over construction of the Green Line's southern extension from Baring to Samut Prakan.
The construction cost is under negotiation.
The BMA could also take the Green Line's extended northern section from Mor Chit to Saphan Mai-Ku Kot as well. However the details would need further study, he said.
A source at the Mass Rapid Transit Authority of Thailand (MRTA) said ACM Prajin would like to have the entire Green Line under BMA supervision.
The BMA already has control over the Green Line project's Mo Chit to On Nut, and National Stadium to Saphan Taksin sections with the Bangkok Mass Transit System Plc (BTSC) being the concessionaire and operator of the route.
The construction of the Baring to Samut Prakan extension was under the MRTA as was development of the Mor Chit Saphan Mai-Ku Kot extension.
However, the Transport Ministry also wants these two extensions under the BMA so construction and running of the entire system can come under a single agency.
If the entire system was overseen by the BMA, all trains could use the BTSC maintenance centre, which would help save the cost of building another centre, the minister said.
He said a single maintenance centre could save up to four billion baht.
Soithip Trisuddhi, permanent secretary for transport, said details of three other electric train projects — the Orange Line (Taling Chan-Thailand Cultural Centre-Min Buri), the Yellow Line (Lat Phrao- Samrong) and the Pink Line (Khae Rai-Min Buri) — will be finalised by next month and forwarded for approval by ACM Prajin and the cabinet.
All could be put up for bidding later this year.
The Purple Line (Bang Yai-Bang Sue), will be finished this year. The service will officially open in 2016.