https://www.facebook.com/nokairlines
"You can share checked baggage weight together (same booking number) but have to check-in at the same time."
http://nokair.com/content/en/nok-care/contact-nok.aspx
Dear Khun Igor,
Thank you for choosing Nok Air!
As your inquiry, please kindly informed that for Nok Economy ticket, passenger may transport free of charge checked baggage weight of 15 kilograms/passenger, and hand baggage must not exceed totally 7 kilograms/passenger and for Nok Flexible ticket, passenger may transport free of charge checked baggage weight of 20 kilograms/passenger, and hand baggage must not exceed totally 7 kilograms/passenger. However, you can share checked baggage weight together (same booking number) and have to check-in at the same time.
Please note that ,if passenger has the excess weight, there will be any charge 300 THB/1 Kilogram for domestic route for excess which passenger must pay at check-in counter when passengers check-in.
Если в одном заказе билетов и вместе регистрируешься, вес может быть общим!