How much is a kilo of overweight luggage of Thai Airways?

You won't buy a baggage claim tag on the spot, starting from 25kg, will you? If so, you'd better buy more baggage tickets according to the actual weight. It's cheap to buy online, so it doesn't matter for two people. Take some in your hand and carry a bag. One person can get on the plane for free, with a small hand luggage, and two people can carry at least 4-50kg of things on their shoulders, plus your minimum reward of 25kg.