Where do you buy your flights for TRs to cancel?

Where do people buy flights with the intention of canceling them for Tourist Visa proof?
I was going to buy an Air Asia one, but it said in the small print they dont give back airport tax to any flight leaving Thailand. Shame because the actual flight was only 100bht, it was basically all airport tax.
its so cheap Ill probably buy anyway, but just wondering if there was a popular one.