Learn Hardcore Croatian: Volim se smijati u parku.

Se is a clitic (an unstressed little word) that follows the “second position” rule in Croatian: it usually wants to stand right after the first stressed word or phrase in the sentence.

Dictionary form: smijati se
In a sentence with another verb, the clitic can move: volim se smijati

Natural:

Volim se smijati u parku. ✅

Unnatural / wrong:

Volim smijati se u parku. ❌ (sounds foreign / ungrammatical)

So the pattern is:

main verb (here: volim)
then clitic (se)
then infinitive (smijati)

Could I just say Volim smijati u parku?

No, not with the intended meaning.

Volim smijati u parku. by itself sounds incomplete or wrong.
It suggests I like to make (someone) laugh in the park, but you have not said whom you make laugh.

If you want to talk about you laughing, you need se:

Volim se smijati u parku. = I like to laugh in the park. ✅

If you want to say you like making others laugh, add an object:

Volim smijati djecu u parku. = I like to make children laugh in the park. ✅

Why is the verb after volim in the infinitive (smijati) and not present tense (smijem)?

In Croatian, when you say you like / want / can / must do something, the second verb is usually in the infinitive:

Volim se smijati. = I like to laugh.
Želim se smijati. = I want to laugh.
Mogu se smijati. = I can laugh.

Volim se smijem would be wrong, because you would be mixing two fully conjugated verbs where Croatian expects one conjugated verb (volim) + one infinitive (smijati).

Why is there no ja (I) in the sentence?

Croatian is a pro‑drop language: the subject pronoun is usually left out because the verb ending already shows the person.

volim clearly tells you it is 1st person singular (I).

So:

Volim se smijati u parku. = I like to laugh in the park.
Ja volim se smijati u parku. is possible, but ja adds emphasis, like:
I (as opposed to someone else) like to laugh in the park.

Why is it u parku and not u park?

The preposition u can take different cases:

u
- locative = location (where?)
  - u parku = in the park
u
- accusative = direction (where to?)
  - u park = into the park

Your sentence describes where you like to laugh (a location), so you use u parku (locative).

Why does park change to parku?

Park is a masculine noun. In the locative singular (used after u for location), masculine nouns usually take the ending -u:

nominative: park (basic dictionary form)
genitive: parka
dative/locative: parku

So:

u parku = in the park (locative)
You cannot say u park for location; that would be accusative and mean into the park (direction).

Can se go anywhere else in this sentence? For example: Volim smijati se u parku or Se volim smijati u parku?

Not freely. Because se is a clitic, it has very strict placement rules.

Correct options:

Volim se smijati u parku. ✅
U parku se volim smijati. ✅
Ja se volim smijati u parku. ✅

Incorrect or very unnatural:

Volim smijati se u parku. ❌
Se volim smijati u parku. ❌

Rule of thumb: se should come right after the first stressed word or phrase in the clause, not after the infinitive.

Does se here mean that I am laughing at myself?

No. In smijati se, se does not literally mean myself. It is just part of the verb pattern smijati se = to laugh.

You can still say smijati se nekome / nečemu:

smijati se nečemu = to laugh at something
smijati se nekome = to laugh at someone

So in Volim se smijati u parku, se is simply required by the verb smijati se and does not by itself mean at myself.

Can I use sviđa mi se instead of volim here?

It is possible, but it sounds a bit different and is less common with a bare verb.

Volim se smijati u parku.
Neutral, straightforward: I like to laugh in the park.
Sviđa mi se smijati se u parku.
Grammatically possible, but feels more like:
I enjoy (the fact that I) laugh in the park / I find laughing in the park pleasant.
It is less idiomatic than volim se smijati.

Voljeti + infinitive is the normal, natural way to say to like doing something.

How would this sentence change with other persons (you, he, we, etc.)?

You keep se smijati, but conjugate voljeti:

Ja volim se smijati u parku. → usually Volim se smijati u parku. = I like to laugh in the park.
Ti voliš se smijati u parku. → Voliš se smijati u parku. = You (sg.) like to laugh in the park.
On / Ona voli se smijati u parku. → Voli se smijati u parku. = He / she likes to laugh in the park.
Mi volimo se smijati u parku. → Volimo se smijati u parku. = We like to laugh in the park.
Vi volite se smijati u parku. → Volite se smijati u parku. = You (pl./formal) like to laugh in the park.
Oni / One vole se smijati u parku. → Vole se smijati u parku. = They like to laugh in the park.

In real sentences, the subject pronoun (ja, ti, on…) is usually dropped unless you want emphasis.

Can I move u parku to the beginning of the sentence, and does that change the meaning?

Yes, you can move u parku for emphasis on where, but the basic meaning stays the same:

Volim se smijati u parku.
Neutral word order, simple statement.
U parku se volim smijati.
Puts more focus on in the park (as opposed to somewhere else).
U parku volim se smijati.
Possible, but less natural than U parku se volim smijati because the clitic se prefers to be early (second position).

So word order is flexible for emphasis, but the placement of se is constrained by the clitic rules.