$20K cash is too much. That exceeds the amount most countries allow you to carry without reporting it at Customs. You'd probably get away with it, but why risk it? And 20K baht isn't enough to buy a ticket home, so that requirement isn't that useful. I aim for $4,900, which is less than the $5K that triggers the reporting requirement (in most of the countries I cross). Over the past 25+ years of traveling and living in Asia, it's saved my bacon on several occasions when the banks back home froze my cards and even closed my accounts because of suspicious activity (and because I no longer had a US mailing address). Travel enough to enough countries and there's a good chance it'll happen, usually at an inopportune time. Cold hard cash (USD, GBP, Euros) can be a lifesaver. Make sure they're new bills and of mixed denominations. I've been saved by a $20 bill when a hotel wanted 500 baht for a key deposit, and I hadn't hit the ATM yet on arrival.