How to Fix the TH Sound: A 7-Day Drill for Vietnamese Speakers

If you're a Vietnamese speaker, the TH sound is the most obvious tell in your accent — and the easiest to fix. English native listeners hear "sink" when you mean "think", and "tink" when you mean "thing". The good news: TH is not hard to pronounce; it's hard to pronounce automatically. This 7-day drill is designed to take you from consciously wrangling your tongue into shape to producing TH without thinking, using the same principle speech therapists apply with adult learners: high-volume repetition with instant feedback.

Why Vietnamese speakers struggle with TH

Vietnamese has no /θ/ or /ð/ sound. The closest equivalents are tʰ (the aspirated "t" in "thì") and d or z (as in "dạ"). When a Vietnamese speaker sees "th" in English, the brain defaults to the closest existing sound, usually a hard t followed by a puff of h — producing "t-hink" instead of "think". The fix is not to learn an entirely new sound from scratch; it's to learn a new tongue position for an airflow you already know how to make.

The two TH sounds you need to know

English has two TH phonemes, and you need to be able to tell them apart.

Voiceless TH /θ/

Your vocal cords do not vibrate. The sound is just airflow between the tongue and the teeth. Examples: think, three, thing, thank, throw, breath, both, tooth, month, south.

Voiced TH /ð/

Your vocal cords vibrate (you can feel the buzz if you put a hand on your throat). Tongue position is identical to /θ/, but you add voicing. Examples: the, this, that, there, mother, brother, other, they, though.

Key point: 80% of the time, Vietnamese speakers substitute a hard t or d for both. Native listeners can usually guess the word from context, but the foreign accent is unmistakable. Mastering the difference between "three" and "tree", or between "this" and "dis", will immediately bump you up a notch in clarity.

Day 1 — Get the tongue position right (15 min)

Stand in front of a mirror. Open your mouth slightly. Place the tip of your tongue so that it just barely peeks out between your upper and lower front teeth. Now breathe out gently. You'll feel cool air on your fingers if you hold them in front of your lips. That's /θ/.

Repeat 30 times. Then add voicing: same position, but turn on your vocal cords (say "zzz" and push the tongue forward between the teeth). That's /ð/.

Words to drill: think, thing, three, throw, thumb, teeth, both, math, breath, tenth, fifth, sixth, month, fourth.

Day 2 — Minimal pairs (20 min)

Minimal pairs are words that differ by only one sound. They're the fastest way to build the ability to discriminate first, then produce.

Read each pair aloud 10 times, alternating between the TH version and the no-TH version. Record yourself. Listen back. The goal is to hear two distinct sounds, not one sound produced with effort.

Day 3 — Function words (15 min)

The small words cause the most trouble in conversation. "I tink so" sounds childish; "I think so" sounds fluent. The most common function words with TH are:

• the (the single most common word in English — appears in 6% of speech!)
• this / that / these / those
• they / them / their / there / then / than
• with (often pronounced as "wid")
• the before consonants: /ðə/ ("the apple")

Practise 10 sentences using these function words. Example: "The thing is, they don't know." / "I went there with my brother." / "This is thicker than that."

Day 4 — Rhythm and connected speech (20 min)

Once you can produce TH in isolation, you need to use it in connected speech. The challenge is that in fast English, TH often weakens to a quick "t" or "d". The trick: keep your tongue forward (between the teeth) even when you're not stressing the word.

Read the following paragraph aloud three times, focusing on keeping your tongue forward for every TH:

"Thirty-three thieves thought they could thieve on Thursday. The thing is, the other thieves thought the same thing. By the time the third thief reached the thicket, the others had already left. So there they were, three of them, with nothing."

Yes, this paragraph is full of TH. That's the point. By the third read your mouth will be tired and you'll be producing TH on autopilot.

Day 5 — Record and self-assess (15 min)

Record yourself reading a passage from a news site (BBC, NPR, Voice of America). Then go through what you said, focusing on every word with TH. Mark each as correct, sloppy, or wrong.

The target is at least 90% of TH words pronounced correctly. If you're below 70%, repeat Day 4. If you're above 90%, you're ready for the integration stage.

Day 6 — Conversation drill (20 min)

Talk with a friend, an AI tutor, or even a voice recorder. Tell a 2-minute story. Then listen back and count your THs. Topics to try: "The third time I went abroad" / "Three things I love about my job" / "A thought I had this week".

The goal is to use TH in spontaneous speech, not just read-aloud. This is where the practice gets harder — and where most of the progress happens.

Day 7 — Test under pressure (15 min)

Watch a 5-minute English video without subtitles. While you listen, repeat every TH word the speaker says in your head. Then turn the video off and talk about the content for 2 minutes, paying attention to your own TH pronunciation.

Or, take a TH discrimination test online (many free ones on YouTube). Target 95%+ correct for both /θ/ and /ð/.

Common mistakes that keep Vietnamese speakers stuck

1. Tongue behind the teeth. The most common error. The tip of the tongue must be visible between the teeth, not behind them. Use a mirror until this becomes automatic.

2. Biting the tongue. Some learners press the tongue too hard against the teeth, producing a stop instead of a fricative. Relax. TH is a continuous sound; the airflow keeps going for 1–2 seconds.

3. Dropping TH in function words. "I went to the store" becomes "I went to e store" — and the listener hears "I went to store" as a grammar error, not a pronunciation error. Function words are your highest-priority targets.

4. Confusing /θ/ and /ð/. "Think" and "this" use two different TH sounds. Practise both. The voiced one requires vibrating vocal cords, which you can feel by putting a hand on your throat.