Tôi muốn mở khóa thẻ.

A natural word-by-word breakdown is:

• Tôi = I
• muốn = want
• mở khóa = unlock
• thẻ = card

So the sentence structure is basically:

• Tôi
  • muốn
    • mở khóa
      • thẻ
• I
  • want
    • unlock
      • card

In natural English, this is usually understood as I want to unlock the card or I want my card unblocked.

In Vietnamese, you usually do not need a separate word equivalent to English to before a verb after muốn.

So:

• muốn mở khóa thẻ = want to unlock the card

This is normal Vietnamese grammar. After muốn, the next verb can come directly.

More examples:

• Tôi muốn ăn = I want to eat
• Tôi muốn đi = I want to go
• Tôi muốn gọi ngân hàng = I want to call the bank

So the lack of to is completely natural.

It is written as two separate written syllables: mở khóa. That is normal in Vietnamese spelling.

Together, mở khóa means to unlock.

Individually:

• mở = open
• khóa = lock

But when used together as a verb phrase, mở khóa means unlock or unblock depending on context.

For a card, mở khóa thẻ often means:

• unlock the card
• unblock the card
• remove the block from the card

So even though the parts literally suggest open + lock, the combined meaning is unlock.

By itself, thẻ is a general word meaning card. It could refer to different kinds of cards depending on context, such as:

• bank card
• ATM card
• credit card
• debit card
• access card
• ID card

If you want to be more specific, you can add another word:

• thẻ ngân hàng = bank card
• thẻ ATM = ATM card
• thẻ tín dụng = credit card
• thẻ ghi nợ = debit card
• thẻ căn cước = ID card / citizen ID card

So if you specifically mean a bank card, Tôi muốn mở khóa thẻ ngân hàng may be clearer.

Vietnamese does not use articles the same way English does. There is no direct equivalent used in every sentence for a, an, or the.

Also, Vietnamese often leaves out possessives like my when the meaning is obvious from context.

So:

• thẻ can mean a card, the card, or my card, depending on the situation.

If you want to make my card explicit, you can say:

• thẻ của tôi = my card

For example:

• Tôi muốn mở khóa thẻ của tôi = I want to unlock my card

But in many real situations, just thẻ is enough because everyone understands you mean your own card.

Grammatically, Tôi muốn mở khóa thẻ most directly means I want to unlock the card.

However, in real-life situations, especially when speaking to a bank or customer service agent, it often works as a polite request meaning:

• I want my card unlocked
• I would like to have my card unblocked

So the exact interpretation depends on context.

If you want to make the someone does it for me meaning clearer, you could say:

• Tôi muốn được mở khóa thẻ = I want my card to be unlocked
• Tôi muốn nhờ mở khóa thẻ = I want to ask for help unlocking the card

But the original sentence is still very natural in a service context.

Vietnamese word order is usually:

• Subject + verb + object

So here:

• Tôi = subject
• muốn mở khóa = verb idea
• thẻ = object

That is why thẻ comes after mở khóa.

Compare:

• Tôi mở cửa = I open the door
• Tôi khóa xe = I lock the bike
• Tôi muốn mở khóa thẻ = I want to unlock the card

So the order is very normal for Vietnamese.

A rough pronunciation guide for English speakers is:

• Tôi ≈ toy but shorter and smoother
• muốn ≈ something like moo-uhn with a rising-ish tone shape
• mở ≈ muh with a broken, dipping tone
• khóa ≈ khwah with a rising tone
• thẻ ≈ teh with a dipping, broken tone

Important note: Vietnamese tones matter a lot, so any English-style approximation is only rough.

The tones here are:

• Tôi — ngang
• muốn — sắc
• mở — hỏi
• khóa — sắc
• thẻ — hỏi

If you are learning pronunciation, it is especially important not to ignore the difference between:

• thẻ
• thè
• thể
• thẹ

They are different words or could sound incorrect if the tone is wrong.

Yes, it is understandable and natural enough, especially in a practical context.

But in customer service, speakers often make it slightly more specific or polite, for example:

• Tôi muốn mở khóa thẻ ngân hàng. = I want to unlock my bank card.
• Tôi muốn mở khóa thẻ của tôi. = I want to unlock my card.
• Làm ơn mở khóa thẻ giúp tôi. = Please help unlock my card.
• Tôi cần mở khóa thẻ. = I need to unlock my card.

So your original sentence is good, but you may choose a fuller version depending on the situation.

No. Tôi muốn mở thẻ khóa is not correct for this meaning.

The correct phrase is mở khóa = unlock.

So:

• mở khóa thẻ = unlock the card

If you change the order, the meaning breaks down and sounds wrong.

This is a good example of how Vietnamese multi-word verbs must keep their normal order.

Here are some common variations:

• Tôi muốn mở khóa thẻ của tôi.
  I want to unlock my card.

• Tôi muốn mở khóa thẻ ngân hàng.
  I want to unlock my bank card.

• Tôi cần mở khóa thẻ.
  I need to unlock the card.

• Làm ơn mở khóa thẻ giúp tôi.
  Please help unlock my card.

• Thẻ của tôi bị khóa. Tôi muốn mở khóa.
  My card is locked. I want to unlock it.

These are all useful in real conversations, especially with bank staff or customer support.