If you are planning to travel in South East Asia (or in China, Korea, Japan in spring and summer), you don't need to pack much. Over the years, I have been trimming my bag as I discover new fabrics, technology etc. This is my current arrangement.
Most important is the bag. The brand doesn't matter as long as it is somewhat waterproof and sturdy. Mine is "Product No 98" by Ichizawa, a Kyoto based canvas bag maker. I like it for its simplicity and utilitarian looks.
The stuff inside - clockwise from 12'o clock
- The black zipper bag contians one or two change of clothes depending on how long my trip is for.
- A notebook - doubles as storage for tickets, maps etc.
- A Kindle - I often carry books set in, or from the countries I am traveling to - makes a good conversation starter
- A transparent mesh bag for toiletries (some airport security like to able to visually inspect stuff)
- The small green zip bag contains quick relief for common ailments - paracetamol and charcoal pills for stomach
- A soft foldable hat - it is waterproof
- Swimwear and a small ziplock bag for when the trunks are wet.
- A water flask
- In the middle we have a small black zipper bag with a charger/cables, a power bank, and a burner phone (good to have these for charge longevity, I usually slot in a voice only prepaid sim from my home region or a region around me with cheapest roaming rates), and a small lock for guesthouse lockers.