You need to have a government issued ID
on you always, unless you are younger than 16 and are with your parents. Being a foreign citizen, you need to have your passport on you, at all times. (Well, you don't need to, but you never know when you will need it). As for air travel, even domestic, if you are a foreign national, you will need a passport on all flights at the point of check-in and security. If you go out of security and want to re-enter, you have to have your passport.
If you are a US citizen, then a valid Driver's License or a Valid Government ID
is perfectly fine for domestic travel. You can also use your passport for domestic travel.
For bars, credit cards, prescriptions, etc., you need a valid passport since you are not a citizen of the US. Also, a hotel will ask you for ID
of some sort, and most likely, it will be your passport since you are not residing in the US.
Many stores and vendors ask for ID
when using a Credit Card or a Debit Card, so you will need an ID
I never leave my house without my ID
, and I live in the US. I feel naked without it.
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way