different immigration offices have different requirements. Pattaya funds need to be in account 2 months before you apply and min of 50% kept there all of the time
this happens SOMETIMES to tourists who are using Thailand as a long term home without a visa, go on a good organised tour and the staff enjoy all runs smoothly. I know several in Pattaya but not Bangkok sorry
I have never heard of that, I have used agents in the past then done things for myself, I don't see why anyone cannot?? Friends also swap agents when they find a promotion too, one only last week