In Singapore, only the older-style ticket machines at MRT stations take foreign cards (the machines that also accept cash). The newer ones don't. Unfortunately, many stations have now replaced all but one of the older machines with the new ones, which is very inconvenient. There was a very long line last week at a station of foreigners buying tickets from the counter, as the only older machine was very well hidden behind a pole!
In Indonesia, cash is absolutely king. As soon as you're out of the city or tourist areas, there is a 0 chance that you can pay with card. The QRIS (Indonesian QR code) can be used in some stores, but it's very much still the minority.
Cambodia, Vietnam, Thailand, Malaysia - all similar to Indonesia, with cash being king. Most local places will not accept cards. Cambodia also accepts USD in addition to KHR, with most prices in Siem Reap tourist areas being listed in USD only and a street exchange rate of 1 USD = 4000 KHR in place.
Of course, if you're just visiting foreigner-oriented places, such as upmarket restaurants, many will accept cards. But what's the point in travelling if you don't actually visit the real country? I don't understand people who visit a country (especially in Asia) and only eat at restaurants. What a waste.