I am not convinced that a thin wallet is good for me. When I am going for easy hikes or even just city walks I take a thin coin purse, pop in a couple of bills, bank card, my transit pass, a chapstick, and my keys. That goes in my front pocket, the phone and headphones in the other, sunglasses on face, and I am good to go.
My regular wallet is a bit of a command centre for me. I have removed unnecessary cards, receipts get removed at the end of the day, if there are too many coins the small ones get tossed into a jar and the big ones go into a piggy bank. That takes a lot of weight off immediately.
I have used the same wallet for years, replacing as they die. Don't know what I will do when this one goes! will have to find a local equivalent.
What always lives in my wallet: Drivers' licence, medical insurance card, residence permit, 3 loyalty cards, bank card, credit cards, paint chip used to match any purchases, book of stamps, 2 safety pins, 2 paperclips, slim pen, emery board, 2 business cards, 2 of my husband's business cards.
I have a small labelled box on my bookshelf that holds wallets/coin purses etc.
I have multiples because we are often in other countries and need other currencies. Eg. when I was regularly going to Hungary this spring, the Forint bifold was ready to go in the morning. Less-used currencies are in labelled envelopes in the same box, ready to be transferred to a wallet. I slip in a small index card with notes jotted about exchange rates for each. For example I use euro, so I would put 1 euro = 275 Forint, 5 euro = (whatever, all the way up to 100 euro). This way I can eyeball approximate costs very fast rather than standing at a counter with my calculator. But I digress.
The wallet-as-command-centre works for me, but it doesn't work unless I carry a bag. So the solution for men would be different!