I know how to fry tofu to make it firm, and also how to dry fry it and marinade it to make it flavorful.  Neither of these cooking techniques mimics the tofu I get at my local Thai restaurant.  When I order tofu there, it is perfectly fried to give it firm texture on the outside, but when you bite in, it's juicy and melts in your mouth, making the tofu experience much better.  It literally blends with the other flavors this way and I can't figure out how they do it.  I'll also note that the inside is not seasoned, it's the internal texture that makes it taste so good.  Is it the type of tofu maybe?  Or the frying time?  Any ideas? 
Do you ever deep fry it, or are you always doing a pan-fry/shallow fry? Most of the tofu I see at Thai restaurants is deep fried, which yields the texture I think you are talking about. You may or may not be willing to deep fry at home, but I think if you do you'll get the result you are looking for. 