Learn Hardcore German: Ich denke manchmal daran, im Ausland zu arbeiten.

When what you are thinking about is not a simple noun, but a clause or an action (like im Ausland zu arbeiten), German normally uses a da- compound (a so‑called prepositional pronoun):

an + das → daran
Ich denke daran, im Ausland zu arbeiten.

You cannot say:

❌ Ich denke an, im Ausland zu arbeiten.

So daran stands for an das, referring forward to the action im Ausland zu arbeiten.
Literally: I think sometimes of that, (namely:) working abroad.

What exactly does daran denken mean? Is it just to think about?

daran denken (from an etwas denken) means to think of / to think about something, often with a nuance of having something in mind or not forgetting it.

In this sentence:

Ich denke manchmal daran, im Ausland zu arbeiten.
→ I sometimes think about working abroad / I sometimes think of working abroad.

It usually does not mean deep reflection or careful consideration. For thinking something over in a more reflective way, German prefers:

über etwas nachdenken – to reflect on something
- Ich denke darüber nach, im Ausland zu arbeiten.
etwas überlegen – to consider something
- Ich überlege, im Ausland zu arbeiten.

So your sentence suggests that the idea of working abroad comes to your mind from time to time, not necessarily that you are carefully planning it.

Why do we need the comma before im Ausland zu arbeiten?

The part im Ausland zu arbeiten is an infinitive clause with zu. In German, such clauses are usually separated by a comma when they depend on another element in the sentence, especially:

on a verb
on words like um, ohne, statt, anstatt, außer, als

Here it depends on daran denken:

Ich denke manchmal daran, [im Ausland zu arbeiten].

German grammar treats im Ausland zu arbeiten almost like a subordinate clause (dass ich im Ausland arbeite), and those are separated with a comma.

So: the comma is obligatory here in standard written German.

What is im Ausland zu arbeiten grammatically? Is it a full clause?

im Ausland zu arbeiten is an infinitive clause with zu (zu + infinitive):

arbeiten – infinitive
zu arbeiten – infinitive with zu
im Ausland zu arbeiten – infinitive phrase with a prepositional phrase (im Ausland) attached

Functionally, this whole phrase acts like the object of daran denken:

Woran denkst du? – Daran, im Ausland zu arbeiten.

The subject of arbeiten is ich, but it is understood from the main clause and not repeated:

Full meaning: Ich denke manchmal daran, (dass ich) im Ausland (sein und) arbeiten (könnte).

So yes, it is a kind of subordinate structure, but it remains non-finite (no personal verb ending), so we call it an infinitive clause, not a full finite clause.

Why is zu used before arbeiten? When do you use zu + infinitive?

German uses zu + infinitive in many subordinate constructions when you talk about actions in a more abstract or non‑finite way, especially after certain verbs, adjectives, or nouns:

Ich versuche, pünktlich zu sein.
Es ist schwer, Deutsch zu lernen.

In your sentence, the infinitive clause depends on daran denken, so you need zu:

Ich denke daran, im Ausland zu arbeiten.

Compare:

With dass-clause (finite):
- Ich denke daran, dass ich im Ausland arbeiten könnte.
With infinitive clause:
- Ich denke daran, im Ausland zu arbeiten.

You do not use zu with:

modal verbs: Ich will im Ausland arbeiten. (not zu arbeiten)
verbs of movement + another verb often just use infinitive: Ich gehe arbeiten.

Here, since arbeiten stands in a dependent infinitive clause with denken, zu is required.

Why is it im Ausland and not in Ausland?

Ausland is a neuter noun (das Ausland, literally: the foreign country / abroad).

With the preposition in, you need a case and usually an article:

in + dem Ausland (dative, location) → contracted to im Ausland

So:

Ich bin im Ausland. – I am abroad. (location → dative im)
❌ Ich bin in Ausland. – incorrect.

The form im is just in + dem merged together, just like:

in dem Haus → im Haus
in dem Park → im Park

What is the difference between im Ausland and ins Ausland?

This is a very common and important contrast:

im Ausland = in dem Ausland (dative): being abroad, location
- Ich war ein Jahr im Ausland. – I was abroad for a year.
ins Ausland = in das Ausland (accusative): going abroad, movement towards
- Ich gehe ins Ausland. – I am going abroad.

So in your sentence:

im Ausland zu arbeiten
→ the emphasis is on the place where the working happens (location), not on the movement there.

Could we leave out daran and say Ich denke manchmal, im Ausland zu arbeiten?

No, not in standard German. That version sounds ungrammatical or at least very wrong to native speakers.

The verb denken in the sense of to think about almost always needs a preposition (an, über, etc.) or a construction like darüber nachdenken:

Ich denke an dich.
Ich denke an meinen Urlaub.
Ich denke daran, im Ausland zu arbeiten.
Ich denke darüber nach, im Ausland zu arbeiten.

Without daran (or without something like darüber nach), denken is usually:

about having an opinion:
- Was denkst du? – What do you think?
about mental activity in general:
- Ich denke viel. – I think a lot.

But to mean I think about working abroad, you must keep a prepositional element:

Ich denke manchmal daran, im Ausland zu arbeiten.
or
Ich denke manchmal darüber nach, im Ausland zu arbeiten.

What is the difference between daran denken and darüber nachdenken in this kind of sentence?

Both are possible with im Ausland zu arbeiten, but they differ slightly in meaning:

daran denken (from an etwas denken)
- Focus: the idea occurs to you, you have it in mind.
- Often lighter, more spontaneous.
- Ich denke manchmal daran, im Ausland zu arbeiten.
  → The idea of working abroad crosses my mind from time to time.
darüber nachdenken (from über etwas nachdenken)
- Focus: reflecting / thinking something over, more deliberate.
- Often sounds more serious or analytical.
- Ich denke manchmal darüber nach, im Ausland zu arbeiten.
  → I sometimes think it over / consider it, to work abroad.

Both are grammatically fine, but darüber nachdenken suggests more active, deeper consideration than just daran denken.

Why is manchmal placed after denke? Could we move it?

manchmal is an adverb meaning sometimes. German adverbs are quite flexible in position. These are all possible and natural:

Ich denke manchmal daran, im Ausland zu arbeiten.
Ich denke daran, manchmal im Ausland zu arbeiten.
Manchmal denke ich daran, im Ausland zu arbeiten.

But:

In your sentence, Ich denke manchmal daran, ..., manchmal modifies denken (the frequency of the thinking).
If you say Ich denke daran, manchmal im Ausland zu arbeiten, manchmal now modifies im Ausland arbeiten (the frequency of the working abroad), i.e. to work abroad sometimes rather than I sometimes think about it.

So you can move manchmal, but be aware that:

Before denke or right after denke → frequency of thinking
Inside the infinitive clause → frequency of working abroad.

What case and gender is Ausland here?

Ausland is:

gender: neuter – das Ausland
in im Ausland, it is dative singular after in with a static location.

The breakdown:

das Ausland – nominative/accusative singular
des Auslandes – genitive singular (rare in everyday speech)
dem Ausland – dative singular

Then:

in + dem Ausland → im Ausland

So in the sentence im Ausland zu arbeiten, Ausland is dative singular neuter.

The sentence is about the future. Why does German use the present tense (denke) and not a future tense?

German often uses the present tense (Präsens) to talk about the future when the context makes the time clear:

Nächste Woche fahre ich nach Berlin. – I am going to Berlin next week.
Ich denke daran, im Ausland zu arbeiten. – I am thinking about working abroad (sometime in the future).

Future tense (Futur I) in German:

Ich werde daran denken, im Ausland zu arbeiten.

is normally used:

for emphasis on the future aspect
for making predictions
in more formal or written contexts

In everyday speech, Präsens + context is more natural. Here, denke in the present describes your current mental state (you now sometimes think about a future possibility).