Yup! Thai custom << See this link for the 40,000 Baht "limit". However upon doing additional research (asking people on the internet) Amazon.com (not Amazon UK) seems to just handle all issues just like MrJ2U said.
Here is a link I posted on reddit regarding this and the response there are pretty much unanimous.
If anyone has actually ordered from Amazon, totalling above 40,000 Baht, Id like to confirm the consensus. I might also just do 2 orders to fly under the radar, as mentioned previously, to avoid the exciting adventure with Thai customs