In my experience in Thailand, if the Bar or Restaurants owners are Farangs with Thai wives, the beer prices will be high for sure ( with very few exceptions).
if they have Bar girls, expect much higher prices, even for a soda water 40 baht (9 in 7 eleven) the girls get no pay, but free accommodation ( usually 5 to a room) and they have to do all the cleaning, cooking and laundry! Then they are taught to push the customer to buy them a drink, they get like a 100 baht for each drink, it can cost the customer 150-200baht, then they sometimes clear off to another customer. Good if you’re on holiday and want some fun and the exchange rate is always favorable.
But beers brewed over here and sold in other bars are very expensive because the government tax them the same as imported beers. Craft beers for example. I paid 200 baht for a small bottle of very good locally brewed IPA. It was very similar to White Shield that you used to get in the UK, supping beer, poured carefully to leave the yeast at the bottom of the bottle.
I love real ale so I pay high prices at special Thai beer cafes, sometimes 240;baht for a decent German stout, the same for a pint of Guinness. Cheap Thai beer is an insult to my kidneys lol