Here is a brief explanation of how to pronounce T, D and R in Hmong.
You place your tongue against the back of your front (top) teeth and make a D sound. This would be identical to ต in Thai. Keep in mind that if there is a puff of air along with it, you are pronouncing the letter ‘TH’ in Hmong.
Next, the D:
You need to move your tongue up slightly from the T and make a D sound. This would be identical to the ด sound in Thai or the T sound in English. Again, if there is a puff of air along with it, it is ‘DH,’ not ‘D.’
Now the R:
With the ‘R’ you need to move your tongue up slightly from the ‘D’ position and make a ‘D’ sound again. However, it should come out sounding more like a ‘DR’ sound, as in the English word, ‘draw.’ It can’t be stressed enough that if a puff of air comes out along with the letter, you are then pronouncing the letter ‘RH,’ not ‘R’