Casual writing to express that someone is thinking of something?

In casual writing we often use the colon to express that people are talking. Example:

Tom: hi
Mary: hi

I'm wondering what about if it is Tom thought of something instead of Tom talking? Like is this valid, or is there a better way to express this:

Tom thought: asdasd

The usual answer is:

(thinks) in braces,

or, in some situations you can use an ellipsis, or, you can use italics,
or you can use < pointy braces >. So, here's the "standard" way...

Tom: I love you.
Tim (thinks): Did he just say that?
Tom: I said I love you, dude!
Tim: Well, whoa!
Tom (thinks): But what next??

I think an ellipsis can work well, particularly in a poetic context, and if you're context is good so it's obvious it's a thought.

Tom: I love you
Tom... what have I said?!
Tim: You .. you love me?
Tim... did he just say that?

And so on. Enjoy!

This form of writing comes out of the idea of a script. Usually in a script any action being undertaken is written before the colon — although these are usually actions, not thoughts, the same principle could work:

Tom: Hi.
Mary: Hi.
Tom (thinking Mary looks more tired than ever today): Are you feeling okay?

Of course this relies on Tom saying something after his thought. If that isn't the case, you can include the action as a separate line in brackets, like this:

Tom: Hi.
Mary: Hi.
(Tom thinks this is going to be a boring conversation.)
Mary: What have you been doing today?