Welcome to FT!

1. Many electrical items purchased in Thailand have only warranty that is effective in Thailand, but some offer 'internatnal warranty' - but maybe also price is higher. I would expect that warranty for Thai TV and blue ray player would not be honoured in India. Please check.

2. You can either buy duty free on departure ( but still expensive) or buy downtown. You can refund the tax at the airport, but it is a bit of a hassle procedure. Note that on arrival in India you may have to pay some tax -I have no idea about that.

Sorry not much help....!