Can't you open another account in Canada even with another bank, then you can get a back-up card. I use one card topped with low funds and have 2 back-ups. Also bring about $3-5k cash and just store in Hotel safe.
Most hotels do month to month. But no real website for this. Agoda does long stays and builds in monthly discounts, best is to ask Hotel when here. As as ruff guide monthly is half the rack rate. So, 800bht/nite would be around 12-14,000b/mth.
DO NOT cancel your USA number. There is too many things tethered to your US number. I switch to pre-paid but almost never use it. Sometimes you need codes sent to your US number, keep a burner phone with you in Thailand and have your US SIM in this phone. Set up a Thai sim in your main phone. If you need to call US number use Skype/What's APP etc.