Thai Airways International has estimated its financial losses at 100 million baht ($3.1 million) a day from flight disruptions due to the volcanic ash cloud in Europe.
The Star Alliance carrier has cancelled flights on nine out of 13 routes to Europe, says the airline's president Piyasvasti Amranand.
A total of 70 flights from 16 to 19 April were cancelled, says Thai, which scrapped flights to London, Frankfurt, Copenhagen, Oslo, Stockholm, Zurich, Munich, Paris and Milan.
However, the airline's flights to Rome, Madrid, Athens and Moscow are not affected.
The carrier is liaising with authorities to operate additional flights to Rome and Madrid to help stranded passengers get to Europe.
It is also hoping to secure approval for flights between Bangkok and Toulouse, as an alternative to the Bangkok-Paris route, adds the airline.
European authorities are planning to re-open sections of airspace from 08:00CET (06:00UTC) today.
About 8,700 flights took place in European airspace yesterday, says Eurocontrol. Flights were allowed in southern and central Europe, as well as parts of northern Europe, it adds.