Decent and economic priced roof constructor sought

As said in the title, I'm looking for a roof constructor do do a quite extensive job at reasonable price. Had an inspection by an expert and the conclusion was that my original constructor did a half arsed job.

So the need is to improve the weldings and maybe here and there make a small reinforcement. Had a price quotation already from a guy, and he quoted 300.000 Baht.

That is labor only, no materials included and probably also little or none needed. He said the job would take a month, so I expect 2 weeks.

Guess he must have a costly life style, or think that all farangs are dumb.

Please note that I'm not looking for an all-round man, but a specific roof worker.