no you can make an international transfer from Bangkok bank and Krungsri to banks outside Thailand but you depend on the banks approval of the transfer (which I got with my 2 test transfers) DeeMoney is good because it generates a qr code so you don't need approval from the Thai bank (depending on your limits etc of course). I mention these 2 banks because I have accounts there - of course other Thai banks also allow it.
just got an account in Krungsri Udon Thani - brought passport and proof of residence from immi (500 baht) - no problem. Kasikorn said no - they wanted a visa stamp in my passport but I had the evisa stamp - very strange