Update 2019-02-28: Flights operated by Thai Airways are scheduled to resume on Thursday (28 February). Flights to Lahore, however, will remain suspended and disruptions are still to be expected on flight routes between Europe and Thailand.
Multiple flights had been cancelled, including flights to London, Munich, Paris, Brussels, Milan, Vienna, Stockholm, Zurich, Copenhagen, Oslo, Frankfurt, and Rome.
Bangkok Post, FCO, Reuters
Update 2019-02-27: Flights from Europe destined for Thailand are affected as well.
2019-02-27: On Wednesday (27 February), Thai Airways announced to cancel all its flights from Thailand destined for Europe. This measure was taken because of the closure of Pakistan's air space.
Passengers are advised to contact their airline or tour operator about the current flight status in advance to their journey to the airport and schedule enough time for their journey.