I live in Thailand (20+ years). This is typical. Take something apart, it's filthy. They try to 'work' on it without even cleaning off the dirt. Years ago a kid at a shop where I'd taken my truck for back brakes started doing that...pulled the drum, the spreader bars, the springs etc. So far, so good. Then he started putting the new shoes on without even cleaning the backing plate. I stopped him, explained what he had to do, and he gave me the typical nasty look then followed my instructions. Thai repairmen treat us farangs (foreigners) like we're all stupid, not knowing that many of us (like me) were working on bikes, then minibikes and motorcycles then cars and trucks before he was born. I don't trust Thai workmen, imagine how I feel about their doctors.