Hi Trung
I would guess that the amount of time for your seedling thai lessard sugar apple trees to fruit would be atleast a couple of years . You also have to factor in the type of care that you're giving them along with the environmental conditions that they are growing in . There's no way to know for sure how long they will take to fruit. I have read different posts where on average it takes 2-3 years. Sugar apples do very good in pots . I have a few seedling sugar apple trees myself in pots and because of our hot summer sun I grew them under shade cloth , they did great under it .
William