This is Thailand, not the UK. Used car prices are manipulated.
Having said that, the average asking price for a 3-4 yo full electric MG ZS is about 650,000 baht.
https://www.one2car.com/en/cars-for-sale/mg/zs?fuel_type=Electric
The 2023 new MG ZS is 1.2 million baht. That's a depreciation hit of about 150,000 baht/year.
I bought a 2 yo Mazda 2 for 440,000 baht. RRP new was 600,000 baht. Depreciation 80,000 baht/year. After 3 more years of my ownership, the insurance company values it at 350,000 baht, my depreciation is 30,000 baht/year.
Obviously, both ICE's and EV's take the biggest hit in their first 2-3 years. After that, the depreciation of an ICE slows down. IMO the asking price of a secondhand EV will continue to fall off a cliff.
Everyone knows what life to expect out of an ICE. Plenty of 20 yo cars on Thai roads. It's too early to tell how many km will be racked up by an EV, which means there will be a lot more buyer hesitancy.