It depends on where you're staying.In rural areas AIS or True, but imo in major cities Dtac is better than True. I'm staying in Jomtien and Dtac is way better than True. Dtac's app is very good, AIS's is ok but True's is a disaster.
I'm banking with both Bangkok Bank and KBank and my daily limit at Bangkok Bank is 2 million baht. I'm not complaining.If using KBanks internet bank K BIZ the transfer limit is much higher than in the app.