54% import tax seems to be correct but, as your quoted article states, there are multiple other taxes added on top of it, i.e. 160bt per bottle excise+local tax + 10% consumption tax for better wines + 7% VAT . Still, even considering all these, I also do not understand how the wine prices here can be averagely 3-4 times higher than in Europe too. And not only on good wines but on cheap ones too. Furthermore, the 54% import tax should not even be applicable for wines from Chile and Australia.
Either way, one can hope that proposed reductions in import tax and excise tax shall result in some reduction in prices eventually.