They are all taken or blocked - no availability. From ARN/CPH there are only 14 seats in C for each flight and TG has no problem filling those seats with revenue pax. However, May/June should be easier as this is low season to Thailand. Your chance is either via OSL (very good availability in C/I class OSL-BKK) or last minute. TG often releases I class seats around one week prior to dep.