The Skytrain and MRT rides I took were packed, standing room only. Also all the platforms and exits were fairly crowded.
So not too easy with luggage to go to the airport, I would imagine.
Also the one Skytrain station has up escalator but stairs going down. Maybe there's an elevator somewhere but didn't look for it.
I'm guessing credit/debit cards aren't too common so the MRT supports contactless cards (but not mobile payments like ApplePay as I understand it) so they use these tokens and RFID cards as tickets on these systems. Can't be cheap for them to deal with the money and then making/recycling the tokens and the cards?
But Thailand, like other Asian countries, seems more cash-oriented and probably credit cards aren't as common as in the US. Otherwise the payment systems for these transit systems seem like they could use modernization, though the turnstiles have RFID readers on them.
But the Skytrain was perplexing, they had kiosks which only accepted coins but fares were often over 20 THB so you need bills to pay? Speaking of cash transactions, at Sala Daeng station I went to the ticket counter to buy a 25 THB ticket with a 500 THB note, the lowest denomination I had. She gave me the ticket and 75 THB in change. I looked at it, paused and she said sorry and gave me 400 THB more.
Honest mistake or she's seeing whether I noticed?
But all these employees that these transport systems have for selling paper or RFID card or token as tickets, that adds to the costs. Even these mini buses had a ticket seller on board in addition to the driver.
So I gather there aren't enough credit or debit cards in circulation to support credit/debit cards as the main payment method?