Tôi tưởng thẻ tín dụng ở trong ví.

In this sentence, tưởng usually means thought / assumed, but it turns out that was wrong.

So Tôi tưởng thẻ tín dụng ở trong ví often implies:

• I thought the credit card was in the wallet,
• but apparently it wasn’t.

That is a very common nuance of tưởng.

By contrast, nghĩ is more neutral:

• Tôi nghĩ thẻ tín dụng ở trong ví = I think the credit card is in the wallet.

So:

• tưởng = I thought/assumed (often mistakenly)
• nghĩ = I think / I thought, more neutral depending on context

Vietnamese often does not need an equivalent of English that in sentences like this.

English:

• I thought that the credit card was in the wallet.

Vietnamese:

• Tôi tưởng thẻ tín dụng ở trong ví.

This is completely normal. Vietnamese often places the whole clause directly after verbs like:

• nghĩ = think
• biết = know
• tưởng = think/assume mistakenly

You do not need to insert anything between tưởng and thẻ tín dụng.

Vietnamese verbs do not change form for tense the way English verbs do.

So tưởng itself does not have a past ending. Time is understood from:

• context
• time words
• the meaning of the verb

Here, tưởng naturally suggests a past or earlier assumption:

• Tôi tưởng... = I thought...

If you want, you can make the time clearer with words like:

• lúc nãy tôi tưởng... = earlier I thought...
• hôm qua tôi tưởng... = yesterday I thought...

But even without them, Tôi tưởng... already sounds natural as I thought...

Here, ở marks location: to be at / in / located at.

So:

• thẻ tín dụng ở trong ví literally means
• the credit card is located in the wallet

This is a very common Vietnamese structure:

[thing] + ở + [place]

Examples:

• Điện thoại ở trên bàn. = The phone is on the table.
• Tôi ở nhà. = I am at home.

In your sentence:

• ở trong ví = in the wallet

Both can be natural, but there is a slight difference in structure.

• ở trong ví = located inside the wallet
• trong ví = in the wallet / inside the wallet

With ở, the sentence clearly uses a location verb:

• Thẻ tín dụng ở trong ví.

Without ở, Vietnamese may still allow:

• Thẻ tín dụng trong ví.

But ở trong ví sounds a little fuller and more explicitly like is in the wallet.

So for learners, ở trong ví is a very safe and natural pattern.

Ví can mean:

• wallet
• purse
• sometimes more generally a small personal case for money/cards

The exact English translation depends on context and the speaker.

So:

• if a man says it, English might often translate it as wallet
• in another context, it could be purse

Vietnamese does not always make that distinction as strictly as English does.

Vietnamese does not use articles the way English does.

So:

• thẻ tín dụng can mean a credit card, the credit card, or credit cards depending on context.

In your sentence, context tells us it is probably:

• the credit card

Vietnamese relies heavily on context instead of words like:

• a
• an
• the

That is very normal.

Good question. Vietnamese classifiers are common, but they are not required in every sentence.

You may hear:

• Tôi tưởng thẻ tín dụng ở trong ví. or
• Tôi tưởng cái thẻ tín dụng ở trong ví.

Both are possible.

The version without cái is perfectly natural, especially in straightforward statements.

Adding cái can:

• make the noun feel more specific
• sound a bit more conversational
• sometimes add emphasis

So:

• thẻ tín dụng = fine and natural
• cái thẻ tín dụng = also fine, with a slightly different feel

Yes, you may hear là after verbs like nghĩ, tưởng, or biết, but in this sentence it is usually more natural to leave it out.

Most natural:

• Tôi tưởng thẻ tín dụng ở trong ví.

Possible:

• Tôi tưởng là thẻ tín dụng ở trong ví.

However, with this kind of sentence, adding là can sound a little less direct or slightly heavier. Learners should usually prefer the version without là unless they have heard a specific pattern they want to imitate.

The overall order is actually quite similar:

• Tôi = I
• tưởng = thought
• thẻ tín dụng = the credit card
• ở trong ví = was in the wallet

So Vietnamese follows a pattern like:

subject + verb + clause

Inside the clause: thing + location phrase

This makes the sentence relatively straightforward for English speakers.

Very often, yes.

Because of tưởng, the sentence often suggests:

• the speaker had that belief,
• but reality turned out differently.

So in many situations, the hidden meaning is something like:

• I thought the credit card was in the wallet, but it isn’t.

That implied contrast is one reason tưởng is so useful.

Yes. Tôi is just the pronoun I, and it is fairly neutral and polite.

You could replace it depending on who is speaking:

• Mình tưởng thẻ tín dụng ở trong ví.
• Em tưởng thẻ tín dụng ở trong ví.
• Anh tưởng thẻ tín dụng ở trong ví.

But the correct pronoun in Vietnamese depends heavily on:

• age
• relationship
• social situation

For learners, tôi is a safe default in many contexts.

A simple approximate pronunciation is:

Tôi tưởng thẻ tín dụng ở trong ví
≈ toy too-uhng teh tin zoong uh chong vee

A few notes:

• tưởng has a dipping/rising tone and is one of the trickier words here.
• thẻ also has a marked tone.
• dụng is pronounced with a z/y-like sound in northern Vietnamese, but more like y in some southern speech.
• ví has a rising tone.

If you are learning standard northern pronunciation, it is especially important to listen carefully to:

• tưởng
• thẻ
• ví

because the tones carry a lot of meaning.

A few natural possibilities are:

• Tôi tưởng thẻ tín dụng ở trong ví chứ.
  This adds a feeling like I thought it was in the wallet though.

• Tôi cứ tưởng thẻ tín dụng ở trong ví.
  Cứ tưởng strengthens the idea of a mistaken assumption:

  • I really thought / I was under the impression that the credit card was in the wallet.

• Tôi tưởng là thẻ tín dụng ở trong ví cơ.
  More conversational, with a bit of emphasis depending on region and tone.

But the original sentence:

• Tôi tưởng thẻ tín dụng ở trong ví. is already natural and correct.