No... it put it my cart for $399 and clipped a $50 the coupon. When the prime day sale started at midnight for $349, the coupon stacked (but was otherwise unavailable). I think I got lucky, and the system was delayed in disabling the coupon for me. Here's the exact link I used – but buyer beware, the seller looks particularly sketchy. It arrives tomorrow and I can update if you'd like (it's returnable if it arrives fucked up).

I found another – $354 less $30 coupon = $324. I realize you're in Singapore, but maybe useful for others. Possibly a sketchy seller too.

For what it's worth, this company has a multiple listings of the same machines. The prices are pretty much the same all the time but they bounce around between their mini-shops. If you miss out on the sale now you can catch it pretty much any time you want by searching for the particular model you're hunting for on DuckDuckGo/Google etc.

Snagged a 5560U a few weeks ago. Using it for emulation & Jellyfin.

Searched my model up and what do you know, it's cheaper on their other page:
https://www.amazon.com/Beelink-SER5-5560U-500GB-Computer/dp/B0B3WYVB2D

Another page from them, same model and also cheaper w/ the $50 click coupon:
https://www.amazon.com/Beelink-SER5-5560U-Computer-Support/dp/B0B2JX2QY7

Same probably goes for these other models.