Despite flying in and out of Bkk for almost every month, I personally didn't face this issue of cutting queue at immigration. All I see is only talking loudly when gathering before immigration.
And why you still join normal queue despite there is automated lane for Bkk?
You know how many PRC visit Thailand per year? And definitely not everyone is so rich like you can visit Paris many times. Most of them is follow tour group and you don't expect tour group to bring you go boutique shop for shopping instead of sightseeing? Even when I at queueing at eiffel tower or Louvre, from far can already hear PRC talking loudly or shouting Liao.
As for customs, there is more and more fraud going on worldwide so is their duty to see all the products brought by passengers not only PRC. They also request to see all my products before in Euro.
The automated lanes are closed whenever I was there. =/ I tend to travel during a specific period and often take the same flight back.
Somehow, they are just very prominent at the airports to me and the worst are always during departure from Suvarnanhumi airport. I am pretty sure there were other tourists who were equally amused and annoyed at the same time from their loud conversations while queueing for immigration. They don't cut queue at immigration but they are bound to do so at tax refund. The group of PRC tourists at the front of the queue will somehow start to expand over time.
Paris's customs seems very lenient towards most tourists regarding tax refund. Whenever there is someone taking stuff out to show the customs officers, it is always a PRC passport holder. Perhaps you have bought too much too? =P
The only time I have ever showed my items for tax refund was at TPE airport where the PRC tourist insisted to watch that the customs officer indeed check every item that was approved for tax refund.