whereabouts in southeast asia?
700c are rarely seen outside of the major cities.
when you do see 'em, they're lime-green 23mm tires on fixies for
schoolkids, or narrow racing tires for the local club riders.

standard is 26", and even then not much selection in the
countryside. mostly your basic knobbly tractor tires.
tubes are hard to find in many places.

few people (mostly kids and peasants) ride bikes, few know
where to find a bike shop. most shops are tiny department
store bike vendors.

you'll need to do some planning beforehand. contact some
bike shops in the big cities.......bangkok, chiang mai, yangon,
siem reap, phnom penh, ho chi minh city. they should be
able to source what you need and express delivery to your
brokedown location.