the 500k was in my account for only the last month of bank statements however i provided 6 months of statements - it seems for softpower applications maybe they are more leniant with how long the money has been in your account here in hanoi?
the gym you apply through will provide you with documents stating they are registered within thailand and that you have paid a deposit or in full for the intended duration of training for the visa they will sign it and provide copies of their id
i seen that others were doing it to use as proof of current location with the vietnam entry stamp i do not think its a neccessity but helps to show that your not just going to try get straight back into thailand whilst you wait for the visa