I
that determiner (demonstrative adjective), demonstrative pronoun, and adverb BrE AmE ðæt —There is no weak form for that in this sense: that ( ðæt ) man, stop that, not that bad .
II
that complementizer (conjunction and relative pronoun): strong form BrE AmE ðæt , weak form ðət —Normally, the weak form is used: say that ( ðət ) she's right, the one that I chose .