Is there any templates or demos available?
It's pretty difficult to make one by myself without any aid.
You could make a text display gui with a bubble graphic
That as easy as displaying the lucasarts-style speech. The only difference is that you can set up a special thinking gui, as LostTraveler mentioned. Consult the manual about a DisplayThought (CHARID, string message) function. The paragraph contains all the info on thinking stuff.
InCreator, I found this in an old post of yours, is it still the problem?
"I managed to create a bubble using text window gui option, but it's kinda lame. And I'd like to see one or two smaller (with decreasing size) cartoony bubbles under the big, text-filled one. Desirably, pointing at the character who's thinking. How is it done?"
I can't help with making a non-lame GUI, but the easiest way to do the 'cartoony bubbles' is to make a thinking view for the character, with the bubbles drawn onto the sprites. That way they'll always be in the right position, and always pointing at the right character.
I'm having trouble making bubble edges for text-gui. transparent color comes into way and leaves pixelwide transparent lines where they are not needed.
Still trying to come across it, though.
I haven't got much time recently, because I'm preparing my game to be something I can put up to games in production forum. Something to screen-shot, i mean.
Here is a template showing bubble GUI in action
http://www.geocities.com/scorpiorus82/bubble.zip (Copy&Paste the link to the address bar!)
Hope it helps
EDIT: to add a copy&paste note