Originally Posted by Pointeater
The most popular ATMs I saw were Siam Bank (purple), Something with a U (orange color), and Bangkok Bank (blue).
What looks like an orange U is a strange geometrical negative outline (what you don't see in the middle is the design it's trying to evoke) of the leaf of the Bodi tree, under which the Lord Buddha reached enlightenment. It's the logo for Siam Commercial Bank.
Bangkok Bank's royal blue logo contains a positive outline of two such leaves, one small and one large on top of one another.
Thai Farmer's Bank has a green logo depicting grains of rice. The name of this bank is now being transliterated into English as Kasikorn Bank, though the meaning is the same.
Krung Thai Bank (transl. City Thai Bank) has a contorted pale blue bird for its logo.
Those four are ubiquitous in Bangkok. To farang like us, they're same same but different. They're all connected to the major world ATM networks and generally don't impose a transaction fee, so you'll only have to pay what your own bank charges. If you want a fleetingly nice feeling, check your bank balance as reported in baht.
Slightly less common are Bank of Ayuddhyah (pale green peaks of sala roofs), Thai Military Bank (I forget what its logo looks like), and one or two others. BofA (if you'll pardon the expression) is also on the world networks, not sure about Thai Military Bank. Discrete square signs bearing the banks' logos sit atop tall scaffold-like towers and dot the Bangkok skyline, so you can almost always find an ATM.
Sathorn Road is the financial center of Bangkok, home to one foreign bank after another. The major Singaporean Banks are there; Citibank is too. If Chase has an office of any sort in Thailand, it's liable to be on Sathorn Road (Chong Nonsi SkyTrain station will get you closest). It may or may not have retail banking, and it may or may not have an ATM. While some of the Singaporeans are making a play for the retail market (UOB comes to mind), Citibank pretty much has only one or two ATM's in Thailand, including in its Sathorn Road office. I would expect Chase to be the same. Notably, "The World's Local Bank," HSBC, does not have much of a retail presence in Thailand.