Yep Samui probably is a bit higher though Hua Hin isn't known for being cheap! Yes twice a week, don't need him more than that and does a really good job. If the heavens open, and the rain can make your pool look crap in hours, he comes around to add chemicals to head it off at no extra charge
It certainly does if you pay well and you've done your homework, references etc. Same as in any country on this planet! But one thing you can be sure of, pay crap money, you'll get a crap job