"Do you still speak with that boy?"
Translation:Tu mai vorbești cu băiatul ăla?
This = acest for masculine singular. It is like any other adjectival declension from there. M plural is acești, F singular is această and F plural is aceste.
Note that these are adjectival form, which is only used preceeding the noun that is being described. Acest băiat. Această fată. If you use "this/these" alone or after the noun, you use the adjectival forms with an 'a' added at the end: acesta, aceștia, aceasta and acestea. Acesta este un băiat. Băiatul acesta.
Note also that you need the definite article ending for the noun if it preceeds this or these. Fata aceasta... legumele acestea.... That/those follows the same patterns, with a little variance on spelling for feminine singular forms.