Usually asian currencies like Indian, Vietnam, cambodia etc has low exchange rates anywhere in the world, it’s not scam when you exchanged from authorized bank, these are their bank’s official rates, always suggested to carry USD
you need to respect people information on forum rather commenting, it’s his/her options to choose best possible commute based on all the information provided by people
IO can decided based on immigration laws, last time when u were 60 days over stay, it should have flagged when you exit, looks like IO over looked it, I assume you should be fine, just keep your fingers crossed, keep some fine money in case they closely look at, good luck