about 300 baht...assuming seller passes on the reduction....
source.... couldn't easily find it without going through loads of documents posted online, but IIRC duty on finished luxury goods was in the order of 300%. so say 1000 baht less sellers mark up of (guessing) 150 baht gives a cost of 850 baht, a quarterof that plus mark up. 300 baht more or less..... plus the usual farang tax.
edit. cut and paste from original article...
These tax cuts are expected to significantly reduce the cost of imported wines in Thailand, a country that has traditionally imposed an average tax of about 250% on wine, including import tariffs, excise tax, municipal tax, and a 7% VAT.