For larger sums nobody sane walks around with a backpack. The normal options are an office visit by appointment, courier delivery to your hotel or condo, or a transfer straight to a Thai bank account, which removes the cash problem entirely. Pick based on what you need the money for. I have used Senate Exchange for
money exchange in Bangkok , they offer office pickup, delivery and bank transfers. Tip: bring your passport for cash operations at an office, it is required, and split a very large exchange over two days if you are nervous about carrying it. Also agree the delivery point clearly if you choose a courier, and be in the room yourself rather than sending a friend. Condo lobbies get confusing and a handover with the wrong person is a problem nobody needs.
