If you have been in Thailand for any length of time, you probably already have the LINE chat app on your mobile phone. I use it every day to communicate with people at work and also with my Thai friends. It is the Asian version of WhatsApp which is popular in the West. But not everyone realizes that this same app also has something called Rabbit LINE Pay. You can use this to pay for goods and services. I signed up for it last year, but I never really used it. However, then I heard that you could link your Rabbit Card for the BTS Skytrain to your Rabbit LINE Pay account. Once you have done this, you never need to queue up ever again to top up your Rabbit Card when riding the Skytrain.
this article on Richard Barrow.