I have had two hernia operations. One in private and one in a public hospital. The public hospital was Queen Sirikit in Sattahip. They used mesh and left no discernable scar.
This was in 2014 and cost 19,000 baht. At the same time I was quoted 120,000 baht for a private hospital. The public hospital was very professional and the only difference, there are not as many spare nurses running around.
The only reason I went to a public hospital was because my health insurance expired as I was waiting for them to okay the cost in a private hospital. One hour after it expired, they contacted me and said no.
I would have no qualms using public again.
Good luck.