You can try him, but I thought I should share my experience so that no one else would have to go through it.
What made it worse is that he kept insisting it was alright, and that he was very experienced. From what I can tell, he basically warped the front crystal gasket so it just won't fit together well anymore. Anyways, it was an old watch, and I went to K2 afterwards and he didn't have spare for the model... And I don't have time for Thong Sia, so well, that's one watch gone forever. Luckily it was a cheap one.
Not sure who else can do this sort of thing.