Fully agree. Normally all airlines state that safety is their number one priority, which makes sense. Having this guy in an enclosed space for 11 hours, not knowing what he was going to do next must have made all the cabin crew nervous.
As this was a long haul flight the aircraft would have had a full loads of fuel, which would have needed dumping before returning to Bangkok, which would be very expensive, but they , Thai Airlines, could have given the Brit the bill!