Meat is sold by the kilo, in open air refrigerated bins.
Have the meat out in the open would not be allowed in any first world countries, but that it the way meat and fish are sold at Lotus’s.
I suspect it is about as hygienic as possible, even though from time to time, you will still see flies on the meat. (Grosses me Out!)
Thai people are use to this and do not seem to mind.
It is another one of those things to learn to live with in rural Thailand.