We live in Pattaya, 2 bed house 10,000 baht, utilities for us are cheap as we only use air con at night. Internet is not that bad. Think this 'friend' could live quite comfortably in Pattaya if they did not go out partying or whoring !
That said, I think life would also depend on what friends overseas status is. If friend has property and a home back in their own country, then life in Thailand would be comfortable as they could basically just spend their money and not need to save anything for emergencies as they could just go home. if you have no easy home return possible then I would suggest saving as much money as possible each month for later years. Potless say 80 in Thailand would be hard if you could not get any health insurance and not return to homeland