Royal Silk Class (business class) passengers are now able to purchase First Class seats on flights where the new preferred seats service is available.
With the introduction to pay for preffered seats in economy, Thai Airways also introduced the concept in business class allowing you to seat in a first class seat, against a fee subject to availability. You will of course only have the first class seat without any first class service.
The preferred seat fee will vary based on flight distance and only be available after tickets have been purchased, subject to availability.
The following table gives you an overview about the prices for the seats and the different zones.