http://www.norwegian.com/en/flight/lowfare/?D_City=BKK&A_City=HEL&TripType=2&D_Month=201406&R_Month=201409&AdultCount=1&ChildCount=0&InfantCount=0&D_Day=1&D_SelectedDay=23&R_Day=1&R_SelectedDay=20
From this link you can ESTIMATE how much do cost flying tickets Bkk-hel-bkk with return.
The embassy demands that must have a ticket with return so only one way reservation is not enough before they let you travel.
This is only one company. Sure is others too. Maybe with a better price.
I willl go to ask from tax office this tax thing. Because 35% is really much to pay.