Står inför samma problem, detta är saxat från deras FAQ:
You can purchase additional baggage allowance at check-in counter on the day you travel. Please make sure that flight date and time of purchase certificate match your travel itinerary.
The additional baggage allowance is calculated per kilogram, starting from 5 kilograms to 10/15/20/25 and 30 kilograms accordingly. One passenger can purchase a maximum of 30 kilograms per destination.
All THAI Smile passengers are entitled to 20 kilograms of checked baggage allowance, and those travelling on Smile Plus class will be received 10 extra kilograms allowance (the total of 30 kgs).
Baggage carried in excess of the free baggage allowance is charged as follows, irrespective of the class paid for and used by the passenger.
Excess Baggage Charge rate, applicable to a checked portion of travel on purely THAI Smile Domestic and International sectors, are in Weight Concept on a fixed rate listed below.
Domestic Route
Between Bangkok and
Khon Kaen/ Udon Thani 55 THB/KG.
Chiang Mai/ Ubon Ratchathani 60 THB/KG.
Surat Thani 65 THB/KG.
Chiang Rai/ Phuket/ Krabi 70 THB/KG.
Hat Yai 80 THB/KG.
Between Chiang Mai and Phuket 125 THB/KG.
International Route
Between Bangkok and Macau 320 THB/KG.
*Remark: Incl. value added tax.