My gf is from Isaan. Has a uni degree. Her spoken English was poor but getting better. Her written English is ok. I just speak Thai mostly as they all understand. Bit hard trying to learn Isaan as well.
In Lao they understood Thai too. Isaan seems to be a slang version of Lao. Rough as you say.
At the start of the 1980s, the average 5ft 3in British female weighed 10 stone (63.5kg), but by now the average weight had increased to 11st 2lb (70.6kg).
https://www.onaverage.co.uk/body-averages/average-female-weight