How to choose materials for a raised bed veggie garden?

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Check out this great article for building a veggie raised garden. https://www.thisoldhouse.com/how-to/how-to-build-raised-vegetable-garden

Use cedar not salt treated wood and for heaven's sake no railway ties even if you used food plastic. Good luck and have fun.

Raised bed but still on the ground, or hanging? Your post is a little confusing about what exactly you're trying to achieve, sorry. Here's what I did though, maybe it'll help? I put in a raised veggie garden in my back yard 2 years ago and used reclaimed wood (you can buy newer that's not treated, or go with pressure treated and seal it with something like thompsons water seal to create a barrier to prevent rot and warping the wood from hose overspray/rain/sun once dried) and built a box with no bottom. Dug up the grass inside and tilled it to make sure I got it all and there wasn't someone's beloved pet or random garbage buried out there and put most of the yard dirt back in. Put down a weed barrier and began filling with gardening soil and remaining dirt to my desired height and planted the seeds and sproutlings then added topsoil and wood chips. When I watered I never had an issue with the garden overflowing or water coming out between the boards as the weed barrier I used still allowed for water to seep through and the roots can still grow down through it. There are different kinds, one is like a heavy plastic sheet and the one I used was lighter and thinner like mesh, kind of reminded me of like thin burlap or a fine mesh window screen. If you hold it up to light you can see the little holes, I honestly can't remember the technical term or brands of these but your local garden center or home improvement store will know what you're talking about. Best of luck!

Depending your age, you could make raised beds so high that you dont need to bend down. (Depending the location of your garden) You can always fill half of your raised garden with cheap straw then top it with good soil. it will be easy on your back and the straw will add warmth from underneath. straw does not rot so easy. make sure the straw is well packed. Cedar wood is great, do not paint the boards on the inside. look up on the internet for combine planting, it will keep your bedding moist longer.

the good Samaritan.

If you want to use treated lumber, just use the plastic garden fabric down the sides to make sure that what it is treated with does not leach into the soil. If your local home improvement store is worth its weight, they should be able to tell you what treated wood is safe for planting vegetables. It is more expensive, but there is marine wood out there that doesn't contain arsenic and it would last for years in the weather. We had to use it when we replace the wood floors in our fishing boat two years ago. You can't use but that on anything that will be covered or stores anything as it can collect and give off the gas that may harm you. The marine wood still looks great after two years of Minnesota weather.