It may be that the daily disposables are not much cheaper in Thailand. They are approx 30 pounds sterling in UK for 30 pairs and that is about the Thailand price. For the monthly disposables I could buy 6 months supply (6 pairs) in the UK from the internet (cheapest source) for approx 35 pounds sterling, whereas it would be about 20 pounds sterling in Thailand. I have bought the Duma monthly disposable lens (which I assume is a local make) and found them very comfortable and the cheapest. I can't remember the exact price but I will be getting some more. I have never heard of a lifetime lens and I can't really see the point (no pun intended).
as you will lose them and damage them thru wear & tear.
I read an article in a well respected UK magazine that the daily disposable lens is almost identical in composition to the monthly disposable so you could in fact buy the dailies and wear them for a month. So 30 months supply for say 30 pounds sterling.