You'll have to show you're bringing in savings that have already been taxed. It is a grey area, but it is live since 1 January 2024. Suggest you consult an accountant familiar with Thai tax law
It's known very well already. Transfers into Thailand from 1.1.2024 are assessable for Thai income tax. Unless your country's DTA exempts your pension, for example. Even then, any liability to Thai tax can be offset by tax already paid on that money
In northern mountains in Winter, maybe some nights would be cool enough. But most nights I think you'd still want at least a fan. BTW here at the coast in Chonburi, I manage with just a big ceiling fan in my bedroom. Very rare I need AC on at night