If anyone is planning to use KTM, you can use Amex by buying your tickets online or via their app. (Have not tried buying it IRL at the counter or tapping at the machines to enter)
And when you're choosing what payment method to use, do not choose credit/international card, but choose debit card/ATM.
Choosing credit brings out the Fiuu/Razer payment page (Amex not accepted), while choosing debit brings out Maybank's check out page.
Then just enter your card details as usual and check out