OK, here's where they show it to you before you buy the ticket. First you put in your cities and dates. On the next page you will see your flight options, and you will choose one (in each direction). Then the next page looks like the picture. See at the lower right where it says "Total Trip Price 165745.00 THB"?

Right below that are five options in blue. (Blue means that they're clickable links.) Click on "Fare rules" and you will see the rules for each fare on your itinerary. You still have not purchased the ticket or given your credit card information at this point, so you can opt out if you don't like the rules for your fare or ticket.