How to pronounce th

Dear Sir,
I am from Viet Nam. I have trouble with "th". Could you please help to guide me the way to pronouce correctly? Where is your tongue stayed?
Thank you and best regards,
Man vo

[Tdol]

Put the tip of your tongue between your teeth.

[Altar_II]

I neither have got this phoneme in my mother tongue, but just by putting the tip of tongue between upper and lower teeth, I learned the pronunciation.
By the way, I guess I have seen this phoneme in some Vietnamese learning website, so, is this phoneme limited to only some dialects in your motherland?

[weiming]

This is kind of silly to be doing online. Even if you were somehow able to understand the explanation of the pronunciation, you might have no way to know if you are doing it right.

But let's try anyway, shall we? You should put the tip of your tonguge (just the tip, not too much) between your teeth (use a mirror, you should be able to see your tongue) and then you force air over your tongue and under your top teeth. Hold this sound for a full second, then say it for shorter and shorter times, then try to put it into words both at the beginning, middle and end of a word.

Also, you must realise that there are two sounds for 'th',

both are fricatives(meaning you make the sound by forcing air through parts of your mouth)
one is voiced (meaning your throat vibrates, or you 'hum' as you say it)
one is unvoiced (there is only the silent hiss of air as you say it)

For more info, please visit this website: .soundsofenglish .org/pronunciation/th.html (add www, remove spaces)

You can find pronunciations for these words in an online dictionary with sound and listen to the difference, and practice it for yourself.

e.g.

(unvoiced) Thick Throat / Without Wrathful / With Hearth

(voiced) Though There / Weather Southern / Breathe Wraith

[gypsy1900]

The only way to make this sound correctly is to put your tongue between your teeth. If this is too difficult for you, you could substitute the 'd' sound for 'th' it's not a perfect solution, but it's easier for speakers of various languages. I have never worked with Vietnamese students.