I recently got a replacement computer from US via Fedex as the original turned up faulty so I sent it back. Since I already paid the Thai customs tax once at Thai Fedex will I have to pay again for replacement or is their a way to avoid this?

If you have paid tax once and can prove it...you dont need to pay tax again

when you sent it out did you use formal customs entry?

Under normal process, it is important to have an record of exporting the faulty computer and the tax records from the first import.

You're probably going to have a fight with those corrupt bastards at FedEx. It is such a good company in the US, I don't know why they put up with the bullshit here. I guess they are in bed with somebody for their priveleges here.

I'll take a hit this time. I ended up replacing it free of charge in USA as original was faulty on delivery/import to Thailand. Fedex Thailand export of original faulty unit only had forms to fill in for US customs to clear and this will be a whole new replacement that is coming back now it seems. One of the extra costs of buying overseas and shipping to Thailand, albeit small vs the savings and product choices.