They're distinct in Indonesian, the former is "solder" while the latter is "las". Most likely a technical assumption made by the author during his visit to the workshop

They're also more or less synonymous in Chinese, resulting in a lot of weird phrases like "infrared welding" or "SMT welding practice kit".

Interesting: How do you express the difference between soldering and welding?

Welding melts the metal to be joined, and joins it with a fillet of the same material.

Soldering does not melt the parts to be joined, it just melts the solder, at a much lower temperature.

Brazing is the midpoint of these: joining with dissimilar metal, without melting the parts to be joined, but at a relatively high temperature.

The GGP said the words for welding and soldering are the same in Portugese. I was asking how people express the difference in Portugese.

Wait what? Is there a distinction for Brazing? There isn't a distinction for the same metals vs different ones?

How about glueing? After all, two parts are held together by application of a different substance.