Saya sangka dia sudah datang.

In this sentence, sangka means thought, assumed, or supposed.

So Saya sangka dia sudah datang means something like:

• I thought he/she had already come
• I assumed he/she had already arrived

It often suggests that your belief may have been wrong, or that you later found out something different.

Both sangka and fikir can relate to thinking, but they are not exactly the same.

• fikir = to think, to consider, to reflect
• sangka = to assume, to suppose, to think something is the case

In this sentence, sangka fits well because the speaker is talking about an assumption or belief about what had happened.

Compare:

• Saya fikir dia akan datang = I think he will come
• Saya sangka dia sudah datang = I thought he had already come

So sangka often sounds more like I was under the impression that...

Sudah means already.

Here it shows that the speaker thought the action of coming had already been completed:

• dia datang = he/she comes / came
• dia sudah datang = he/she has already come / had already come

So sudah adds the idea of completion.

Malay does not mark tense on the verb the way English does.

The verb datang stays the same. Time is usually shown by:

• context
• time words
• aspect words like sudah

So in Saya sangka dia sudah datang:

• sangka gives the idea of a past thought
• sudah shows the coming was seen as completed

English translates this with past forms like thought and had come, but Malay does not change the verb itself.

The structure is:

• Saya = I
• sangka = thought/assumed
• dia sudah datang = he/she had already come

So the sentence is basically:

• I thought [that] he/she had already come

Malay often keeps a straightforward subject-verb-clause order.

You can think of it as:

• Saya
  • sangka
    • dia sudah datang

Yes, in English you could say:

• I thought that he/she had already come

Malay often leaves out a word equivalent to that in this kind of sentence.

So Saya sangka dia sudah datang is completely natural without anything extra.

Sometimes Malay can use bahawa, but in everyday speech it is usually not needed here.

Yes. Dia is gender-neutral in standard Malay.

So this sentence can mean either:

• I thought he had already come
• I thought she had already come

The gender is understood from context.

Datang literally means come, but in many contexts it can also be translated naturally as arrive.

So:

• dia sudah datang can mean he/she has already come
• in natural English, it may also be he/she has already arrived

Which translation sounds better depends on context.

Yes, you can say Saya sangka dia datang, but the meaning becomes less clear and less natural in this context.

Without sudah, it may sound like:

• I thought he/she was coming
• I thought he/she came

With sudah, the meaning is more clearly:

• I thought he/she had already come

So sudah is very useful here.

Yes, telah is possible:

• Saya sangka dia telah datang

This is grammatical, but telah is usually more formal or written in tone.

• sudah = common, everyday, very natural
• telah = more formal, more written

In normal conversation, sudah is usually the better choice.

Yes, it is natural and correct.

It sounds like normal spoken or written Malay. In casual conversation, speakers may also shorten things depending on context, but this full sentence is perfectly natural.

Usually, saya is kept, especially in standard Malay.

Malay sometimes drops subjects in casual conversation when the meaning is obvious from context, but for learners it is best to keep it:

• Saya sangka dia sudah datang

That is clear, natural, and complete.

This is a very common learner question because both can sometimes translate as think.

• sangka = assume, suppose, be under the impression
• ingat = remember, or sometimes think/believe in colloquial use

For this sentence, sangka is the better standard choice if you mean I assumed/I thought.

If you use ingat, it may sound more colloquial in some contexts:

• Saya ingat dia sudah datang

This can also mean I thought he/she had already come, especially in speech, but ingat also has the core meaning remember, so learners should be careful.

A simple pronunciation guide is:

• Saya ≈ SAH-yuh or SAH-ya
• sangka ≈ SANG-kah
• dia ≈ DEE-ah
• sudah ≈ SOO-dah
• datang ≈ DAH-tang

Very roughly:

SAH-yuh SANG-kah DEE-ah SOO-dah DAH-tang

The ng in sangka and datang is like the sound at the end of sing.

Often, yes.

Saya sangka... frequently suggests that this was your assumption, and it may turn out to be false.

For example:

• Saya sangka dia sudah datang, rupa-rupanya belum.
• I thought he had already come, but actually he hadn’t.

However, by itself, the sentence does not absolutely prove you were wrong. It just tells us what you thought. The rest depends on context.