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.
those are still not dirt cheap. If we focus just on generics, every drug that I've ever been prescribed that is available as a generic cost a lot more here, at a Thai pharmacy, than what it would have cost at a Publix supermarket pharmacy in the US.
maybe for drugs that are still on patent but generic meds located though apps like GoodRx in the US are almost always cheaper than at Thai pharmacies, often by a lot.