That is not how it was taught to me. Expat is when your job moves you to a new country, as in "you're an expatriate employee". Immigrant is when you move for your own reasons. Expats are expected to come back to their original country, or move to a third one at some time. Immigrants are establishing themselves in the new country.

Expats usually don’t have immigrant visas. They also receive packages from their companies for their temporary assignments. If you go to the country on your own to fund a job, you usually won’t be referred to as an expat by those with packages who refer to themselves as expats. But you won’t be referred to as a migrant worker either unless you are poor and doing construction or farm work. We used the term half-pats to describe ourselves, but mostly it was just foreigners.

The USA is exceptional because almost every visa that allows for work is considered an immigration visa (eg H1 leads to a greencard, eventually). But in other countries that is most definitely not true.

Or "backpackers" - which seems to be secret code for: stay away, these people (usually guys) cause more trouble than they are worth.

My interpretation has always been that an expat is abroad temporarily, while an immigrant intends to stay permanently.

I came to the US as an expat, but became an immigrant.

If you tend to see racism behind every raised eyebrow, you can of course also see this terminology as racist.