Hello, Can anyone differentiate pronouncing 'A' as in 'as' and 'ha' as in 'has'? I substitute 'as' with 'has'

I am always substitution words beginning with certain vowels, like 'a' and 'e' with 'ha' and 'he' when i pronounce them. For example, I will pronounce ‘asked’ as ‘hasked’ This is getting embarring. Can anyone help with differentiating the difference when pronouncing the words?