Should "in" be used in this ex: I am interested in working abroad or I am interested working abroad. Or both are correct?
I am interested in working abroad.
When you omit the in, you are "interested" and you are "working abroad", but there is no relationship between them. So conceptually in is necessary.
In this example, the phrase is interest in. See interest:
- variable noun
If you have an interest in something, you want to learn or hear more about it.
While in some cases prepositions can be omitted, in is not a preposition in your example.