I honestly just noticed this new registration requirement for the BTS Rabbit Cards,
effective February 15, 2019. FWIW, I have ~ 4 cards, unregistered, and have topped all four them up since that date, so YMMV. There are large signs notifying customers of this at each service window. You can link a Line account to an existing BTS Rabbit card (registration still required) via LINE Rabbit Pay.
Starting Friday BTS ‘Rabbit Card’ holders must register their ID cards
As of Friday, all BTS Skytrain “Rabbit Card” holders are required to register their Thai identification cards or passport numbers as well as contact information with train operators.
“By law, your Rabbit Card is a form of electronic payment, and as such you are required to register your card,” reads a message on the train system operator’s website, citing the 1999 Anti-Money Laundering Act.
When asked why a 20-year-old law is only now being enforced, an employee we reached via the 24-hour Rabbit Card hotline said he had “no idea.”
https://coconuts.co/bangkok/news/sta...ster-id-cards/