It depends upon the amount that you're sending. For USD-THB transfers, assuming that you elect for the currency conversion to be done on the receiving end, above a certain size transaction a bank wire will be more economical than usong Wise. You should be able to work out the math - Thai banks have their current exchange rate for income wires on their web sites (it's the TT rate), you know the flat rate that your US bank will charge and Wise shows you the exact amount of Baht that you'd receive. Compare the two on that basis.
If it's really SSI and not SSDI that you're receiving, you won't be able to collect that if they know that you are living outside the US. However a potentially even bigger problem if you have a disability that requires ongoing medical care is that neither Medicaid nor Medicare will pay for medical care received abroad and you're not going to be eligible for Thailand national healtcare plan.
SSDI is the disability program that is financed by social security and eligibility is a function of your work history. SSI is a disability program that is a companion to Medicaid and to qualify you need to be essentially flat broke and be a resident of the United States. If you're poor enough to qualify for that you probably wouldn't be able to afford a plane ticket to Thailand anyway.
Definitely you can continue to collect Social Security. As for the disability payments, that depends upon their source. If it's SSI, that's a program for low income residents and is funded by general tax revenue rather than by Social Security contributions. Once you're not resident of any state, you can't collect that anymore. If it's SSDI, that's funded by Social Security contributions and eligibility for that is based upon your work history. In that case, if you move abroad similar rules apply as for Social Security.
check the prices on GoodRx, that shows thing cost at supermarket pharmacies and chain drug stores in the US and for genetic (off patent) drugs the prices are usually lower than the prices at independent pharmacies in Thailand.
those probably sell for pennies in the US too. Prices that I see on GoodRx have always been a lot lower than here on the drugs that I've needed. I've encountered some spectacular examples firsthand, such as Temozolomide pills (a chemo drug) costing roughly $3000 per month at Chiang Mai Ram Hospital versus $600 at Northside Hospital in Atlanta.