Iam looking to import sports supplements and need some advice on the custom side of things concerning the Thai end of things. …….any advice would be much appreciated.

Google it, customs have a website where you can find many answers on your questions.

I have looked into it too the problem is its a hit and miss and you can get taxed up to 40%. This is why its hard to build a business. There are some people who know people at customs and get it cheaper. Then its hard to beat those prices.