Last week, we posted on Lexus’ planned major lineup revamp, which will see its GS, ES, IS and LS sedans either redesigned or re-engineered by spring 2013. This, plus a halo “LFA Roadster”, will work to address flagging sales in the crucial North American market.

First out will be the new GS, which will be launched at the Pebble Beach Concours d’Elegance on August 18 – a teaser is already out, click here to view it. The production car should retain much of what we see on the LF-Gh Hybrid Concept from the New York show earlier this year – in line with Lexus’ push for a more dynamic image. For the GS, out goes the soap bar shape for sharper BMW E60 style styling.

Around since 2005, the current GS has its smallest engine pegged at 3.0 litres (GS 300), but reports from Thailand say that the new model will have a smaller 2.5-litre V6 engine to better compete with BMW’s 5-Series and Mercedes’ E-Class. This logical move means that for the first time in the GS’ 20-year history, the car will have an engine smaller than 3.0 litres.

This move will allow Lexus to dodge Thailand’s maximum excise tax of 50% for cars with more than 220 hp (GS 300 has 229 hp), allowing it to be priced at “the level of its intended rivals”. The Thai assembled BMW 523i Highline and Mercedes-Benz E250 CGI Avantgarde sell for 4.249 million and 4.299 million baht, respectively. The current Japan made GS 300 is priced between 5.39 million and 5.99 million baht, putting it out of contention.

Lexus already has a 2.5 V6 in its IS compact exec, so this is no big issue. Perhaps Malaysia is part of the plans as well, since we have a road tax system based on engine capacity, and our market is used to mid sized execs with relatively small engines.

The fourth-generation GS will make its first appearance in our region later this year at Thailand’s Motor Expo.