It can be said “Tha” or “Tha’s”.
E.G.
“Is tha goon doon tay si thi fitba oon Satoorday” (I say are you going to the football on Saturday)
"Tha’s nobbut missen " (There is nobody but myself)
All clear now hin? 
Incidentally I am not from the North East (Geordieland) I’m from the North West where we talk reet proper me 'owd cock
I teach many, many students from West London, primarily black (a fair few of these are of Somali origin) or Asian (by which I mean Indian, Pakistani, Bangladeshi origin). So the accent is very familiar to me. They are for the most part able/willing to moderate it according to the situation, often switching to a very different accent, if needs be.