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

If you are a Vietnamese speaker, the TH sound is the single most recognisable marker of your accent — and also the single most fixable. Native English speakers hear "sink" when you mean "think", and "tink" when you mean "thing". The good news is that TH is not hard to produce; it is just hard to produce automatically. This 7-day drill is designed to take you from conscious tongue gymnastics to unconscious production, using the same principle speech therapists use with adult learners: massive repetition with immediate feedback.

Why Vietnamese speakers struggle with TH

Vietnamese has no /θ/ or /ð/ sound. The closest equivalents are tʰ (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 available sound, which is usually a hard t followed by an aspirated h — producing "t-hink" instead of "think". The fix is not to learn a new sound from scratch; it is to learn a new tongue position for an airflow you already know how to produce.

The two TH sounds you need

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 your tongue and 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 your hand on your throat). The tongue position is identical to /θ/, but you add voice. Examples: the, this, that, there, mother, brother, other, the (article), they, though.

The trick: 80% of the time, Vietnamese speakers replace both with a hard t or d. Native listeners can usually guess the word from context, but the accent is unmistakable. Mastering the difference between "three" and "tree", or "this" and "dis", will instantly move you up a level of clarity.

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

Stand in front of a mirror. Open your mouth slightly. Place the tip of your tongue so it just barely sticks out between your upper and lower front teeth. Now blow air out gently. You should feel cold air on your finger if you hold it in front of your lips. That is /θ/.

Repeat 30 times. Then add voice: same position, but turn on your vocal cords (say "zzz" and move your tongue forward between your teeth). That is /ð/.

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

Day 2 — Minimal pairs (20 minutes)

Minimal pairs are words that differ by only one sound. They are the fastest way to build discrimination, then production.

Read each pair out loud 10 times, alternating between TH and non-TH versions. Record yourself. Listen back. The goal is to hear two different sounds, not one with effort.

Day 3 — Function words (15 minutes)

The little words hurt you most in conversation. "I tink so" sounds childish; "I think so" sounds fluent. The most common function words with TH are:

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

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

Day 4 — Sentence rhythm and connected speech (20 minutes)

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" sound. The trick: keep the tongue forward (between the teeth) even when you are not emphasising the word.

Read this paragraph aloud three times, focusing on keeping the 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 is the point. By the third reading, your mouth will be tired and you will be making TH automatically.

Day 5 — Record and self-evaluate (15 minutes)

Record yourself reading a paragraph from a newspaper or a news website (BBC, NPR, Voice of America). Then transcribe what you said, focusing on every TH word. For each one, mark it correct, sloppy, or wrong.

Aim for at least 90% of TH words produced correctly. If you are below 70%, repeat Day 4. If you are above 90%, you are ready for the integration phase.

Day 6 — Conversation practice (20 minutes)

Talk to a friend, an AI tutor, or even a voice memo. 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 reading aloud. This is where the practice gets harder — and where most of the progress happens.

Day 7 — Test under pressure (15 minutes)

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

Alternatively, take an online TH discrimination test (many are free on YouTube). Aim for 95%+ correct on both /θ/ and /ð/.

Common mistakes that keep Vietnamese speakers stuck

1. Tongue behind the teeth. The most common error. The tongue tip 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 rather than a fricative. Relax. TH is a continuous sound; air keeps flowing 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 the highest-priority targets.

4. Confusing /θ/ and /ð/. "Think" and "this" use different TH sounds. Practice both. The voiced one requires vocal cord vibration, which you can feel by placing a hand on your throat.