If you go to www.thalys.com on Tuesdays there is a last minute 50% discount offer on tickets for selected journeys for the week ahead (Wed-Tue), if you're flexible with train times. Tuesday is the best day to purchase these tickets as availabilty for these tickets is highest. Less seats available on Fridays and Sundays. Amsterdam-Paris is only €47 one way. You can pay with an international credit card and even print your own ticket.