هاي قصة بتضحك كتير.

A common Levantine pronunciation is:

hāy 'iṣṣa btiḍḥak ktīr

A few notes:

• هاي = hāy
• قصة is often pronounced 'iṣṣa in many urban Levantine accents, because ق may become a glottal stop. In other accents, you may hear qiṣṣa or giṣṣa.
• بتضحك = btiḍḥak
• كتير = ktīr

Two sounds that may feel unfamiliar:

• ض in بتضحك is a heavy/emphatic d
• ح is a strong breathy h from the throat

هاي means this.

In this sentence, it is the demonstrative pointing to قصة:
هاي قصة = this story

In many Levantine varieties, هاي is used with feminine nouns, and قصة is feminine. Depending on the country or city, you may also hear other forms like هيدي or هالقصة.

Because in Arabic, especially in the present tense, you usually do not say a word for is/am/are.

So instead of saying something literally like This story is very funny, Arabic often says something closer to:

This story makes you laugh a lot

That is completely normal.
This kind of sentence is called a nominal sentence in Arabic: the subject comes first, and the description follows, without a present-tense is.

قصة is a feminine noun. One big clue is the ending ـة.

Because it is feminine, words connected to it often show feminine agreement. That is why you get:

• هاي for this
• بتضحك in a form that matches a feminine singular subject

So the grammar is agreeing with قصة.

Here بتضحك means something like:

• is funny
• makes you laugh
• gets laughs

Very literally, it is based on the verb ضحك related to laughing.

So the sentence is not word-for-word the same as English funny, but the idea is the same. In everyday Levantine, saying something بيضحك / بتضحك is a very natural way to say it is funny.

Also, even though the verb form can look like you laugh in other contexts, here the subject is clearly قصة, so it means the story is funny / the story makes people laugh.

The بـ is the regular Levantine marker for the present/imperfective tense.

So:

• بتضحك = it is funny / it makes people laugh / it laughs
• without بـ, the form would sound incomplete in normal everyday Levantine, or it might belong to a different structure

This بـ is very common in Levantine verbs:

• بكتب = I write / I am writing
• بيحكي = he speaks
• بتضحك = she/it is funny, makes people laugh

Because it agrees with قصة, which is a singular feminine noun.

In Levantine, the present-tense form for she/it (feminine) is often the same shape as the form for you (masculine singular), so context matters.

Here the subject is stated explicitly:

هاي قصة → this story

So بتضحك is understood as it (the story) is funny / makes people laugh, not you laugh.

It can feel like either one, depending on how you translate the whole sentence.

Literally with the verb, it is closer to:

makes people laugh a lot

But in natural English, that often becomes:

is very funny

So in this sentence, كتير adds intensity. It means the story is not just funny, but really funny.

Yes. Some common alternatives are:

• هالقصة بتضحك كتير = This story is very funny
• القصة هاي بتضحك كتير = This story is very funny
• هاي قصة مضحكة كتير = This is a very funny story

A small nuance:

• بتضحك sounds very natural and conversational
• مضحكة is also correct, but can sound a bit more direct or slightly less colloquial depending on context

A natural MSA version would be:

هذه قصة مضحكة جدًا

You could also say:

هذه القصة تضحك كثيرًا

But the most straightforward MSA equivalent is usually مضحكة جدًا.

So the original sentence sounds clearly Levantine because of things like:

• هاي instead of هذه
• the spoken-style present verb بتضحك
• كتير instead of كثيرًا / جدًا