Just read it Lars
Booking of Seats
5.1
Confirmation of Booking: The booking of a Seat is confirmed after full payment of the fare is made and after we issue you a booking number and/or the Itinerary. Once confirmed, the booking cannot be cancelled and payments made are not refundable.
And change of booking is 900 baht per ticket
I need some Rosso, and lots of it
Edit
Also, since I booked, the tickets have now increased in price on one trip. More to pay.
Dammit, I will write off the £250 and learn from it, never ever again book a LCC with conditions like these.