I did a little digging as I'm sure most of us here must've never heard of this shop, here is what I've found so far.
Taken from tomntoms.co.th:
TOM N TOMS is the global food and beverage franchise company from Korea and with more than 380 outlets over countries in the world including United States, Australia, China, Singapore, Thailand and Vietnam.
And this is from their korean website:
Notice the red box, it counts up to 40 page with 10 outlets per page. I'm counting about 397 outlets if this were true. Jiyeon's ads is most likely only exclusive to Korean outlets but I gotta say 397 coffee shops? That's not bad at all. At least we know Tom n Toms is a big household name.
This is only a rough estimation so it might not be 100% accurate, please take it with a grain of salt.