North Sukumvit has many auto shops. I've found this place to be top notch for batteries. It's opposite the Cholchan Hotel.
12.985838077046838, 100.92242276019981
It is a Thai place, pretty dirty, but there is lots of parking, they speak good English, have a great selection, good prices and good service.
You may get that "hole in the wall" feeling, but you're just buying a battery, not renting an apartment for your mom.
This is Thailand by the way, if you want all the comforts of your home country I kindly suggest you just move back there. Meanwhile, since you're here, you may as well get used to it and then you may find the benefits of living here.
I mean, your message could read,
"I'd like to buy a battery but I'd also like to pay extra to help the shop keeper with is rent and air con bills"
This shop changed my alternator and countless batteries. They have way more knowledge and experience than the new hires at those chain stores. And they get the job done FAST.
I recommend Panasonic batteries, they seem to be the highest quality.
Also, look at the cold cranking amps, (not the battery weight lol). Try to get the higher cranking amps if it's an option.
Vroom Vroom.