The four lines are Purple Line (Chalong Ratchatham Line), Blue Line (Chaloem Ratchamongkon Line), Yellow Line (from Lad Phrao to Samrong stations), and Pink Line (from Kae Rai to Minburi stations).
The move aims to celebrate Songkran Festival, the Thai traditional new year, when Thais pay respect to their elders while reuniting with their families, Wittaya Phanmongkol, acting MRT governor, said on Wednesday.
April 13 is officially Songkran Day and National Elderly Day, while April 14 is observed as Family Day.
Eligible passengers must present evidence at ticket booths of any of the four stations to get a coupon. Each coupon can be used by one person during said period only.
MRTA will also increase security staff during the Songkran holidays to ensure safety of all passengers. K-9 units and EOD (explosive ordnance disposal) teams will be on standby, while security officials will monitor CCTV surveillance 24 hours a day.
Train commuters are urged to cooperate with officials in baggage checking, and not to bring buckets or water guns to the train system.
The authority expects that the free-ride promotion will attract families to use the train system to visit attractions in Bangkok, as well as venues that host religious and water-splashing activities.