box/package

Drones are accepted as carry-on baggage and checked baggage...
If drone’s box is over hand-carry baggage size, it has to be loaded as checked baggage with the maximum of 3 dimensions of package at 158 cm.
Source: Thai Smile Airways, Baggage Policy

Does the package refer to the box?

Yes--the box along with any packaging/covering it may have.

Thank you, Barque.

The longest side of that box can't be longer than 158 centimeters.

kentix said:

The longest side of that box can't be longer than 158 centimeters.

Not exactly. The sum of all three dimensions cannot be more than 158 cm. The package, could, for example, be a perfect cube with each side measuring 52.66 cm. If it measures 100 cm in one direction, the sum of its other two measurements must not be more than 58 cm. If it is 158 cm long, it must be a thin line with no width or height.

(I have enough experience with airlines to know that the sum of all three dimensions is the usual way they describe the size of an item.)