Thai Fisherman's Pants or simply Fisherman Pants are loose fitting cotton pants which are sold in Thailand, Laos, South-West China and maybe other parts of South East Asia.
They are true "one size fits all" as they are extra wide and tied at the waist, extra material is rolled down over the belt to control the length. Thus they are great for maternity wear, La petite mort's sister swears by them.
They are extremely popular with Farangs in Thailand and backpacker culture has brought them as far as Israel, Australia and (In wordnerd's words) "even here in frigid Colorado" to be worn as an alternative to sharwals.
They usually come in one solid pastel color and seem to be unusually popular in purple, bright green and red. They of course come in all the more 'standard' colors as well.
Their light and 'airy' feel makes them ideal for hot climates and comfortable for almost any activity not requiring better protection, while still looking respectable enough to walk into most establishments without looking as if you just came in from the beach.
While called Fisherman's Pants, they are actually Farmer pants and are traditionally made of cotton and dyed with indigo There is also a loose buttoned shirt to go with them. They are usually worn at "flood pants" length.
Thanks for updates from La petite mort, anthropod and wordnerd which were virtually cut and paste from their messages.